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AUSCERT External Security Bulletin Redistribution
ESB-2018.0898.3
Cisco IOS and IOS XE Software Bidirectional Forwarding
Detection Denial of Service Vulnerability
19 July 2021
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Catalyst 4500 Series Switches
Cisco Catalyst 4500-X Series Switches
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2018-0155
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-bfd
Revision History: July 19 2021: Clarified support for the BFD feature per platform
July 10 2018: Source added some clarifications.
March 29 2018: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS and IOS XE Software Bidirectional Forwarding Detection Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-20180328-bfd
First Published: 2018 March 28 16:00 GMT
Last Updated: 2021 July 16 13:31 GMT
Version 1.3: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvc40729
CVE Names: CVE-2018-0155
CWEs: CWE-388
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 Bidirectional Forwarding Detection (BFD) offload
implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst
4500-X Series Switches could allow an unauthenticated, remote attacker to
cause a crash of the iosd process, causing a denial of service (DoS)
condition.
The vulnerability is due to insufficient error handling when the BFD header
in a BFD packet is incomplete. An attacker could exploit this vulnerability
by sending a crafted BFD message to or across an affected switch. A
successful exploit could allow the attacker to trigger a reload of the
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-20180328-bfd
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 the following Cisco products if they are running
a vulnerable release of Cisco IOS Software or Cisco IOS XE Software and the
BFD feature is enabled:
Catalyst 4500 Supervisor Engine 6-E (K5) ^ 1
Catalyst 4500 Supervisor Engine 6L-E (K5) ^ 1
Catalyst 4500 Supervisor Engine 7-E (K10) ^ 2
Catalyst 4500 Supervisor Engine 7L-E (K10) ^ 2
Catalyst 4500E Supervisor Engine 8-E (K10) ^ 3
Catalyst 4500E Supervisor Engine 8L-E (K10) ^ 4
Catalyst 4500E Supervisor Engine 9-E (K10) ^ 5
Catalyst 4500-X Series Switches (K10) ^ 2
Catalyst 4900M Switch (K5) ^ 1
Catalyst 4948E[-F] Ethernet Switch (K5) ^ 1
1. BFD feature support as of Cisco IOS Software release 15.1(1)SG
2. BFD feature support as of Cisco IOS XE Software release 3.5.0E
3. BFD feature support as of Cisco IOS XE Software release 3.6.0E
4. BFD feature support as of Cisco IOS XE Software release 3.8.1E
5. BFD feature support as of Cisco IOS XE Software release 3.10.0E
This vulnerability can be exploited only if the BFD feature is enabled on
an affected device. The BFD feature is enabled by default in Cisco IOS
Software and Cisco IOS XE Software if the software is running an IP Base (
ipbase ) package license or a higher license. The BFD feature is not
supported by a LAN Base ( lanbase ) package license. For more information,
see LAN Base, IP Base, and Enterprise Services Image Support .
For information about which Cisco IOS and IOS XE Software releases are
vulnerable, see the Fixed Software section of this advisory.
Determining Whether the BFD Feature Is Enabled
To determine whether the BFD feature is enabled on a device, administrators
can use the show running-config | include feature bfd command in privileged
EXEC mode. The following example shows the output of the show
running-config | include feature bfd command on a Cisco Catalyst Switch
that has the BFD feature disabled:
switch# show running-config | include feature bfd
platform module all feature bfd disable
platform module feature bfd disable
platform feature bfd disable
feature bfd disable
Empty output from the show running-config | include feature bfd command
would indicate that the BFD feature is enabled.
Determining Which Package License Is Enabled
To determine which package license is enabled on a device, administrators
can use the show license feature command in privileged EXEC mode. The
following example shows the output of the show license feature command on a
Cisco Catalyst Switch that has the IP Base ( ipbase ) package license
enabled:
C4500# show license feature
Feature name Enforcement Evaluation Clear Allowed Enabled Right...
------------------------------------------------------------------------------
entservices true true true false true
ipbase true false true true false
lanbase false false true false false
internal_service true false true false false
If a software release does not support the show license feature command,
administrators can determine which package license is enabled on a device
by identifying the type of software image that is currently running on the
device. To identify the type of software image that is running on a device,
administrators can use the show version | include image command in
privileged EXEC mode. The following example shows the output of the show
version | include image command on a Cisco Catalyst Switch that is running
a software image that has the LAN Base ( lanbase ) package license enabled:
C4948E# show version | include image
System image file is "bootflash:cat4500e-lanbasek9-mz.151-2.SG3.bin"
Determining the Cisco IOS Software Release
To determine which Cisco IOS 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 Software, the system banner displays text similar to
Cisco Internetwork Operating System Software or Cisco IOS Software . The
banner also displays the installed image name in parentheses, followed by
the Cisco IOS Software release number and release name. Some Cisco devices
do not support the show version command or may provide different output.
The following example shows the output of the command for a device that is
running Cisco IOS Software Release 15.5(2)T1 and has an installed image
name of C2951-UNIVERSALK9-M :
Router> show version
Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Mon 22-Jun-15 09:32 by prod_rel_team
.
.
.
For information about the naming and numbering conventions for Cisco IOS
Software releases, see the Cisco IOS and NX-OS Software Reference Guide .
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 the Cisco
Catalyst 4500 Series Supervisor Engine V-10GE (K2) or the Cisco Catalyst
4948 Switch (K2).
Cisco has also 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.
Administrators who do not use the BFD feature in their environments can
disable the feature by using the feature bfd disable command in global
configuration mode. The feature bfd disable command is available in Cisco
IOS Software Releases 15.2(1)E and later and Cisco IOS XE Software Releases
3.5.0E and later.
Administrators who do use the BFD feature in their environments can
implement Control Plane Policing (CoPP) to allow processing of BFD packets
from known BFD peers only and drop all other BFD traffic to limit exposure.
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 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.
Action Links for This Advisory
o Cisco IOS and IOS XE Software Bidirectional Forwarding Detection Denial of
Service
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-bfd
Revision History
o +---------+--------------------------+-------------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+--------------------------+-------------+--------+-------------+
| | Clarified support for | Vulnerable | | |
| 1.3 | the BFD feature per | Products | Final | 2021-JUL-16 |
| | platform. | | | |
+---------+--------------------------+-------------+--------+-------------+
| | Corrected affected | | | |
| | products information in | | | |
| | the machine readable | | | |
| | portion of this advisory | | | |
| 1.2 | (CVRF, OpenVuln API). No | - | Final | 2021-JUL-08 |
| | changes to the textual | | | |
| | security advisory or | | | |
| | Cisco IOS Software | | | |
| | Checker. | | | |
+---------+--------------------------+-------------+--------+-------------+
| | Clarified the licensing | | | |
| | requirements for the BFD | Vulnerable | | |
| 1.1 | feature. Clarified | Products | Final | 2018-MAR-28 |
| | availability of the | and | | |
| | "feature bfd disable" | Workarounds | | |
| | command. | | | |
+---------+--------------------------+-------------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2018-MAR-28 |
+---------+--------------------------+-------------+--------+-------------+
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