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AUSCERT External Security Bulletin Redistribution
ESB-2018.0902
Cisco IOS XE Software for Cisco Catalyst Switches IPv4
Denial of Service Vulnerability
29 March 2018
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Catalyst 3850
Cisco Catalyst 3650
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2018-0177
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-ipv4
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Cisco Security Advisory
Cisco IOS XE Software for Cisco Catalyst Switches IPv4 Denial of Service
Vulnerability
High
Advisory ID: cisco-sa-20180328-ipv4
First Published: 2018 March 28 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs:
CSCvd80714
CVE-2018-0177
CWE-19
CVSSÂ 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 IP Version 4 (IPv4) processing code of Cisco IOS XE
Software running on Cisco Catalyst 3850 and Cisco Catalyst 3650 Series
Switches could allow an unauthenticated, remote attacker to cause high CPU
utilization, traceback messages, or a reload of an affected device that
leads to a denial of service (DoS) condition.
The vulnerability is due to incorrect processing of certain IPv4 packets.
An attacker could exploit this vulnerability by sending specific IPv4
packets to an IPv4 address on an affected device. A successful exploit
could allow the attacker to cause high CPU utilization, traceback messages,
or a reload of the affected device that leads to a DoS condition. If the
switch does not reboot when under attack, it would require manual
intervention to reload the device.
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-20180328-ipv4
This advisory is part of the March 28, 2018, release of the Cisco IOS and
IOS XE Software Security Advisory Bundled Publication, which includes 20
Cisco Security Advisories that describe 22 vulnerabilities. For a complete
list of the advisories and links to them, see Cisco Event Response: March
2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication.
Affected Products
o Vulnerable Products
This vulnerability affects Cisco Catalyst 3850 and Cisco Catalyst 3650
Series Switches that are running Cisco IOS XE Software Release 16.1.1 or
later, until the first fixed release, and are configured with an IPv4
address.
For more information about which Cisco IOS XE Software releases are
vulnerable, see the Fixed Software section of this advisory.
Determining the Cisco IOS XE Software Release
To determine which Cisco IOS XE Software release is running on a device,
administrators can log in to the device, use the show version command in
the CLI, and then refer to the system banner that appears. If the device is
running Cisco IOS XE Software, the system banner displays Cisco IOS
Software, Cisco IOS XE Software, or similar text.
The following example shows the output of the command for a device that is
running Cisco IOS XE Software Release 16.2.1 and has an installed image
name of CAT3K_CAA-UNIVERSALK9-M:
ios-xe-device# show version
Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Sun 27-Mar-16 21:47 by mcpre
.
.
.
For information about the naming and numbering conventions for Cisco IOS XE
Software releases, see the Cisco IOS and NX-OS Software Reference Guide.
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this
vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS
Software, Cisco IOS XR Software, or Cisco NX-OS Software.
Details
o This vulnerability is triggered by certain IPv4 packets that are sent to an
affected device. The same IPv4 packets that are sent through the device do
not trigger this vulnerability.
Indicators of Compromise
o If an exploit has occurred, the device CPU usage will be high, as shown by
the show process cpu sorted CLI command. Depending on the CPU usage, this
information may be available only from a console connection, as remote VTY
sessions may not be possible. Specifically, the IOSXE-RP Punt Se process
will be the one that is consuming the CPU, as shown in the following
example:
Cat3850# show process cpu sorted | ex 0.00
CPU utilization for five seconds: 96%/66%; one minute: 61%; five minutes: 20%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
117 21796 90021 242 40.19% 21.51% 6.27% 0 IOSXE-RP Punt Se
203 153 6311 24 0.07% 0.04% 0.02% 0 IP ARP Retry Age
73 3448 1141 3021 0.07% 0.24% 0.55% 0 IOSD ipc task
200 174 6311 27 0.07% 0.05% 0.04% 0 IPAM Manager
Cat3850#
Workarounds
o There are no workarounds that address this vulnerability.
If the device has high CPU usage for the IOSXE-RP Punt Se process, try to
identify the source of the IP traffic and prevent that address from sending
the packets to the affected device, by either filtering the source address
or removing the source device from the network.
To recover the device, shut down the interface that the IPv4 packets are
being received on, eliminate the source of the attack via an infrastructure
access control list or other methods, and re-enable the interface.
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.
Fixed Releases
This vulnerability is fixed in Cisco IOS XE Software Releases Denali
16.3.4, Everest 16.5.1a, Everest 16.5.2, Everest 16.6.1, and later.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker,
that identifies 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 this tool to perform the following tasks:
Initiate a search by choosing one or more releases from a drop-down
list or uploading a file from a local system for the tool to parse
Enter the output of the show version command for the tool to parse
Create a custom search by including all previously published Cisco
Security Advisories, a specific advisory, or all advisories in the most
recent bundled publication
To determine whether a release is affected by any published Cisco Security
Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a
Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2
or 3.13.8S--in the following field:
[ ] [Check]
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.
Subscribe to Cisco Security Notifications
o Subscribe
Related to This Advisory
o Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
Cisco Security Blog: Cisco IOS and IOS XE Software Bundled Publication
March 2018
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-ipv4
Revision History
o
+----------+----------------------------+----------+---------+----------------+
| Version | Description | Section | Status | Date |
+----------+----------------------------+----------+---------+----------------+
| 1.0 | Initial public release. | -- | Final | 2018-March-28 |
+----------+----------------------------+----------+---------+----------------+
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