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AUSCERT External Security Bulletin Redistribution
ESB-2020.1940
Cisco IOS and IOS XE Software denial of service vulnerability
4 June 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS and IOS XE Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-3225
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cipdos-hkfTZXEx
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev2-9p23Jj2a
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ssh-dos-Un22sd2A
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sip-Cv28sQw2
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snmp-dos-USxSyTk5
Comment: This bulletin contains five (5) Cisco Systems security advisories.
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS and IOS XE Software Common Industrial Protocol Denial of Service
Vulnerabilities
Priority: High
Advisory ID: cisco-sa-cipdos-hkfTZXEx
First Published: 2020 June 3 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvo17827 CSCvp56319 CSCvr47365 CSCvr67776
CVE-2020-3225
CWE-20
CVSS Score:
8.6 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o
Multiple vulnerabilities in the implementation of the Common Industrial
Protocol (CIP) feature of Cisco IOS Software and Cisco IOS XE Software
could allow an unauthenticated, remote attacker to cause an affected device
to reload, resulting in a denial of service (DoS) condition.
The vulnerabilities are due to insufficient input processing of CIP
traffic. An attacker could exploit these vulnerabilities by sending crafted
CIP traffic to be processed by an affected device. A successful exploit
could allow the attacker to cause the affected device to reload, resulting
in a DoS condition.
Cisco has released software updates that address these vulnerabilities.
There are no workarounds that address these vulnerabilities.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-cipdos-hkfTZXEx
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes 23 Cisco
Security Advisories that describe 25 vulnerabilities. For a complete list
of the advisories and links to them, see Cisco Event Response: June 2020
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
These vulnerabilities affect Cisco IOS and IOS XE Software if they are
configured for CIP. CIP is not enabled by default.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine Whether CIP Is Enabled
An administrator can determine whether CIP is enabled on a device by
issuing the show cip status command and checking the State: value.
The following show cip status output shows that CIP is enabled for VLAN 1:
Device>show cip status
State : Enabled
Vlan : 1
If the command returns no output, the device is not affected by the
vulnerabilities described in this advisory.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by these vulnerabilities.
Cisco has confirmed that these vulnerabilities do not affect Cisco IOS XR
Software or Cisco NX-OS Software.
Workarounds
o There are no workarounds that address these vulnerabilities.
Fixed Software
o
Cisco has released free software updates that address the vulnerabilities
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerabilities that are
described in this advisory.
Source
o These vulnerabilities were found during the resolution of a Cisco TAC
support case.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Related to This Advisory
o Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-cipdos-hkfTZXEx
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-JUN-03 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------------------------------------------------------------
Cisco IOS and IOS XE Software Internet Key Exchange Version 2 Denial of Service
Vulnerability
Priority: High
Advisory ID: cisco-sa-ikev2-9p23Jj2a
First Published: 2020 June 3 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvp44397
CVE-2020-3230
CWE-20
CVSS Score:
7.5 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o
A vulnerability in the Internet Key Exchange Version 2 (IKEv2)
implementation in Cisco IOS Software and Cisco IOS XE Software could allow
an unauthenticated, remote attacker to prevent IKEv2 from establishing new
security associations.
The vulnerability is due to incorrect handling of crafted IKEv2 SA-Init
packets. An attacker could exploit this vulnerability by sending crafted
IKEv2 SA-Init packets to the affected device. An exploit could allow the
attacker to cause the affected device to reach the maximum incoming
negotiation limits and prevent further IKEv2 security associations from
being formed.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-ikev2-9p23Jj2a
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes 23 Cisco
Security Advisories that describe 25 vulnerabilities. For a complete list
of the advisories and links to them, see Cisco Event Response: June 2020
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices that are running a vulnerable
release of Cisco IOS or IOS XE Software and have IKEv2 features configured.
Devices configured with only IKEv1 features are not affected.
For information about which Cisco IOS and IOS XE releases are vulnerable,
see the Fixed Software section of this advisory.
Many features can use IKEv2, including different types of VPNs such as the
following:
LAN-to-LAN VPN
Remote-Access VPN, excluding SSL VPN
Dynamic Multipoint VPN (DMVPN)
FlexVPN
Group Encrypted Transport VPN (GET VPN)
Assessing Whether IKEv2 Is Enabled
1. Assess whether the device is configured with IKE (version 1 or 2)
Administrators can use the show ip sockets or show udp EXEC command in the
CLI to see if IKE processing is enabled (this will show for both IKEv1 and
IKEv2 as both use the same port numbers). If UDP port 500, UDP port 848,
UDP port 4500, or UDP port 4848 is open on a device, the device is
processing IKE packets.
The following example shows the output of the show udp command on a device
that is processing IKE packets on UDP port 500 and UDP port 4500, using
either IP Version 4 (IPv4) or IP Version 6 (IPv6):
router# show udp
Proto Remote Port Local Port In Out Stat TTY OutputIF
17 --listen-- 192.168.130.21 500 0 0 1001011 0
17(v6) --listen-- UNKNOWN 500 0 0 1020011 0
17 --listen-- 192.168.130.21 4500 0 0 1001011 0
17(v6) --listen-- UNKNOWN 4500 0 0 1020011 0
.
.
router#
If the command returns no output, or the command returns an error, then the
device is not vulnerable. If the device returns output for any of the above
mentioned UDP ports for IKE then proceed to the next step.
2. Assess whether the device's IKE configuration is using IKEv2
If the show udp command shows that the device is listening for IKE traffic,
an administrator can assess if the device is configured to use IKEv2 by
entering the CLI command show running-config | include ikev2|gikev2 . If
the command returns output, the configuration is most likely set up to
process IKEv2 or G-IKEv2 traffic and is therefore affected.
Note : Some customers may have entered IKEv2 commands but never associated
them with appropriate features. Reviewing the full configuration or
examining the output of the various show crypto ikev2 CLI commands can help
determine if IKEv2 is properly configured.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
Software or Cisco NX-OS Software.
Details
o Cisco IOS and IOS XE Software support IKEv2 for IPv4 and IPv6
communications. IKEv2 communications can use the following UDP ports:
UDP port 500
UDP port 848, Group Domain of Interpretation (GDOI)
UDP port 4500, Network Address Translation Traversal (NAT-T)
UDP port 4848, GDOI NAT-T
An attacker could exploit this vulnerability by using IPv4 or IPv6 on any
of the UDP ports in the preceding list. Traffic needs to be targeted at the
affected device.
Workarounds
o There are no workarounds that address this vulnerability.
If the device has hit the max-in-negotiation-sa limits and they are not
clearing automatically, there is no way to clear the in-negotiation queue.
The only way to recover the device is to power-cycle it. If the source of
the attack has been identified and stopped, an administrator can increase
the size of the max-in-negotiation-sa queue to allow the device to function
until a power cycle can be scheduled by increasing the configured
max-in-negotiation-sa queue as shown in the following example:
Router#configure terminal
Router(config)#crypto ikev2 limit max-in-negotiation-sa 300
Router(config)#end
Router#
Fixed Software
o
Cisco has released free software updates that address the vulnerability
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Related to This Advisory
o Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-ikev2-9p23Jj2a
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-JUN-03 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------------------------------------------------------------
Cisco IOS and IOS XE Software Secure Shell Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-ssh-dos-Un22sd2A
First Published: 2020 June 3 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvp79333
CVE-2020-3200
CWE-371
CVSS Score:
7.7 AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o
A vulnerability in the Secure Shell (SSH) server code of Cisco IOS Software
and Cisco IOS XE Software could allow an authenticated, remote attacker to
cause an affected device to reload.
The vulnerability is due to an internal state not being represented
correctly in the SSH state machine, which leads to an unexpected behavior.
An attacker could exploit this vulnerability by creating an SSH connection
to an affected device and using a specific traffic pattern that causes an
error condition within that connection. A successful exploit could allow an
attacker to cause the device to reload, resulting in a denial of service
(DoS) condition.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-ssh-dos-Un22sd2A
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes 23 Cisco
Security Advisories that describe 25 vulnerabilities. For a complete list
of the advisories and links to them, see Cisco Event Response: June 2020
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices that are running a vulnerable
release of Cisco IOS or IOS XE Software and are configured to accept SSH
connections.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Assessing the SSH Server Configuration
To determine whether the SSH server has been enabled in the Cisco IOS or
IOS XE Software configuration, use the CLI command show ip ssh , and
examine the first line of output, which will report the status as either
Enabled or Disabled.
Here is an example of the output of the show ip ssh command on a router
where SSH is disabled:
Router#show ip ssh
SSH Disabled - version 2.0
Here is an example of the output of the show ip ssh command on a router
where SSH is enabled:
Router#show ip ssh
SSH Enabled - version 2.0
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
Software or Cisco NX-OS Software.
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o
Cisco has released free software updates that address the vulnerability
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Related to This Advisory
o Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-ssh-dos-Un22sd2A
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-JUN-03 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------------------------------------------------------------
Cisco IOS and IOS XE Software Session Initiation Protocol Denial of Service
Vulnerability
Priority: High
Advisory ID: cisco-sa-sip-Cv28sQw2
First Published: 2020 June 3 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvq26057
CVE-2020-3226
CWE-20
CVSS Score:
8.6 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the Session Initiation Protocol (SIP) library of Cisco
IOS Software and Cisco IOS XE Software could allow an unauthenticated,
remote attacker to trigger a reload of an affected device, resulting in a
denial of service (DoS) condition.
The vulnerability is due to insufficient sanity checks on received SIP
messages. An attacker could exploit this vulnerability by sending crafted
SIP messages to an affected device. A successful exploit could allow the
attacker to cause the affected device to reload, resulting in a denial of
service condition.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-sip-Cv28sQw2
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes 23 Cisco
Security Advisories that describe 25 vulnerabilities. For a complete list
of the advisories and links to them, see Cisco Event Response: June 2020
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco routers that are running a vulnerable
release of Cisco IOS or IOS XE Software with any of the following features
configured:
Cisco Unified Border Element (CUBE)
Cisco Unified Communications Manager Express (CME)
Cisco IOS Gateways with Session Initiation Protocol (SIP)
Cisco TDM Gateways
Cisco Unified Survivable Remote Site Telephony (SRST)
Cisco Business Edition 4000 (BE4K)
For information about which Cisco IOS and Cisco IOS XE releases are
vulnerable, see the Fixed Software section of this advisory.
Assessing Whether a Device Is Vulnerable
To determine whether a device is vulnerable, administrators can use the
show processes | include CCSIP_SPI command in the CLI and look for the
presence of the CCSIP_SPI_CONTRO process. The following example shows the
output of the show processes | include CCSIP_SPI command on a device that
has at least one of the affected features enabled and is vulnerable:
Router#show processes | include CCSIP_SPI
671 Mwe 561F108FE8BA 10 11 909234584/240000 0 CCSIP_SPI_CONTRO
Empty output of this command indicates that none of the affected features
are enabled and the device is not vulnerable.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
Software or Cisco NX-OS Software.
Workarounds
o There are no workarounds that address this vulnerability.
However, customers who do not use any SIP features but who have other
voice-related features enabled, which automatically enables the SIP
processes in Cisco IOS and IOS XE Software releases prior to Release 16.11,
can shut down the SIP ports by issuing the following commands in global
configuration mode:
Router(config)#sip-ua
Router(config-sip-ua)#no transport udp
Router(config-sip-ua)#no transport tcp
Router(config-sip-ua)#no transport tcp tls
Alternatively, customers can block traffic targeted to the designated SIP
ports using infrastructure access control lists (iACLs). Using iACLs is a
network security best practice and should be considered as a long-term
addition to good network security as well as a mitigation for this specific
issue. To help protect all devices with IP addresses in the infrastructure
IP address range, customers are advised to include the following iACL
example as part of the deployed iACL:
!---
!--- Feature: SIP
!---
!--- Permit trusted SIP sources.
!---
!--- Permit additional Layer 3 and Layer 4 traffic destined for infrastructure
!--- address space as dictated by existing security policies and configurations.
!--- Permit/deny to infrastructure IP addresses in accordance with security policy.
!---
!--- Deny SIP traffic from all other sources destined
!--- to infrastructure addresses
!---
access-list 150 deny udp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5060
access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5060
access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5061
!---
!--- Permit/deny all other Layer 3 and Layer 4 traffic in
!--- accordance with existing security policies and
!--- configurations. Permit all other traffic to transit the
!--- device.
!---
access-list 150 permit ip any any
!---
!--- Apply access-list to all interfaces (only one example
!--- shown)
!---
interface GigabitEthernet 2/0
ip access-group 150 in
For further guidelines and recommendations for deployment techniques for
iACLs, see the white paper Protecting Your Core: Infrastructure Protection
Access Control Lists and the Cisco Guide to Harden Cisco IOS Devices .
Note : By default, SIP uses UDP and TCP port 5060 for SIP and TCP port 5061
for SIP over TLS. However, these ports are user-configurable using the
listen-port non-secure <port_number> and listen-port secure <port_number>
commands in voices service voip > sip configuration mode. If custom SIP
ports have been configured, the UDP and TCP ports in the previous example
iACL would need to be adjusted accordingly.
Fixed Software
o
Cisco has released free software updates that address the vulnerability
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
Source
o This vulnerability was found by Puspalatha S of Cisco during internal
security testing.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Related to This Advisory
o Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-sip-Cv28sQw2
Revision History
o +---------+---------------------------+---------+--------+---------------+
| Version | Description | Section | Status | Date |
+---------+---------------------------+---------+--------+---------------+
| 1.0 | Initial public release. | - | Final | 2020-June-03 |
+---------+---------------------------+---------+--------+---------------+
- --------------------------------------------------------------------------------
Cisco IOS and IOS XE Software Simple Network Management Protocol Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-snmp-dos-USxSyTk5
First Published: 2020 June 3 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvk71355
CVE-2020-3235
CWE-118
CVSS Score:
7.7 AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o
A vulnerability in the Simple Network Management Protocol (SNMP) subsystem
of Cisco IOS Software and Cisco IOS XE Software on Catalyst 4500 Series
Switches could allow an authenticated, remote attacker to cause a denial of
service (DoS) condition.
The vulnerability is due to insufficient input validation when the software
processes specific SNMP object identifiers. An attacker could exploit this
vulnerability by sending a crafted SNMP packet to an affected device. A
successful exploit could allow the attacker to cause the affected device to
reload, resulting in a DoS condition.
Note: To exploit this vulnerability by using SNMPv2c or earlier, the
attacker must know the SNMP read-only community string for an affected
system. To exploit this vulnerability by using SNMPv3, the attacker must
know the user credentials for the affected system.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-snmp-dos-USxSyTk5
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes 23 Cisco
Security Advisories that describe 25 vulnerabilities. For a complete list
of the advisories and links to them, see Cisco Event Response: June 2020
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco Catalyst 4500 Series Switches that are
running a vulnerable release of Cisco IOS or IOS XE Software, are
configured for SNMP polling, and have Power over Ethernet (PoE) line-card
modules installed.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Assess the SNMP Configuration
To determine whether a device is configured for SNMP, administrators can
use the show run | include snmp command in the CLI. If any output is
returned, SNMP is enabled on the device. The following example shows the
output of the show run | include snmp command on a device that is
configured with both read-only and read-write community strings:
Router# show run | include snmp
snmp-server community public RO
snmp-server community write RW
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
Software or Cisco NX-OS Software.
Details
o An attacker could exploit this vulnerability by sending a crafted SNMP
packet to an affected device by using IPv4 or IPv6. Only traffic that is
directed to an affected system can be used to exploit this vulnerability.
To exploit this vulnerability by using SNMPv2c or earlier, the attacker
must know the SNMP read-only community string for an affected system. A
community string is a password that is applied to a device to restrict both
read-only and read-write access to SNMP data on a device. These community
strings, as with all passwords, should be chosen carefully to ensure that
they are not trivial. They should be changed at regular intervals. They
should also be changed in accordance with network security policies, such
as when a network administrator changes roles or leaves the organization.
To exploit this vulnerability by using SNMPv3, the attacker must know the
user credentials for an affected system.
Workarounds
o There are no workarounds that address this vulnerability.
However, administrators can mitigate this vulnerability by disabling the
affected MIB, in this case CISCO-POWER-ETHERNET-EXT-MIB . To create or
update a view entry and disable CISCO-POWER-ETHERNET-EXT-MIB ,
administrators can log in to the device and use the snmp-server view global
configuration command in the CLI, as shown in the following example:
snmp-server view SNMP_VIEW_NAME ciscoPowerEthernetExtMIB excluded
To apply the configuration to an SNMPv2 community string, administrators
can use the following command:
snmp-server community mycomm view SNMP_VIEW_NAME RO
To apply the configuration to an SNMPv3 community string, administrators
can use the following command:
snmp-server group v3group v3 auth read SNMP_VIEW_NAME write SNMP_VIEW_NAME
SNMP Access Control List
Administrators can reduce the attack surface by using an access control
list (ACL) to restrict SNMP queries from specific IP addresses. However,
administrators are advised to also use Unicast Reverse Path Forwarding
(uRPF).
Since the vulnerable feature uses UDP as a transport, an attacker could
spoof the IP address and bypass an ACL that permits communication to these
UDP ports from trusted IP addresses. The following is an example of an ACL
that allows only hosts at 192.0.2.1 to query the device with SNMP requests:
access-list 1 permit 192.0.2.1
snmp-server community example RO 1
Fixed Software
o
Cisco has released free software updates that address the vulnerability
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Related to This Advisory
o Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-snmp-dos-USxSyTk5
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-JUN-03 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------END INCLUDED TEXT--------------------
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