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AUSCERT External Security Bulletin Redistribution
ESB-2018.0915
Cisco IOS and IOS XE Software Forwarding Information Base
Denial of Service Vulnerability
29 March 2018
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2018-0189
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-FIB-dos
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco Security Advisory
Cisco IOS and IOS XE Software Forwarding Information Base Denial of Service
Vulnerability
Medium
Advisory ID: cisco-sa-20180328-FIB-dos
First Published: 2018 March 28 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs:
CSCva91655
CVE-2018-0189
CWE-399
CVSSÂ Score:
6.8 AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the Forwarding Information Base (FIB) code of Cisco IOS
Software and Cisco IOS XE Software could allow an unauthenticated, network
attacker to cause a denial of service (DoS) condition.
The vulnerability is due to a limitation in the way the FIB is internally
representing recursive routes. An attacker could exploit this vulnerability
by injecting routes into the routing protocol that have a specific
recursive pattern. The attacker must be in a position on the network that
provides the ability to inject a number of recursive routes with a specific
pattern. An exploit could allow the attacker to cause an affected device to
reload, creating a DoS condition.
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-FIB-dos
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices that are running a vulnerable
release of Cisco IOS Software or Cisco IOS XE Software.
For information about which Cisco IOS and IOS XE Software releases are
vulnerable, consult the Cisco bug ID(s) at the top of this advisory.
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 Cisco IOS XR
Software or Cisco NX-OS Software.
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o For detailed information about fixed software releases, consult the Cisco
bug ID(s) at the top of this advisory.
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.
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.
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
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-FIB-dos
Revision History
o
+----------+----------------------------+----------+---------+----------------+
| Version | Description | Section | Status | Date |
+----------+----------------------------+----------+---------+----------------+
| 1.0 | Initial public release. | -- | Final | 2018-March-28 |
+----------+----------------------------+----------+---------+----------------+
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