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AUSCERT External Security Bulletin Redistribution
Cisco IOS and IOS XE Software Internet Key Exchange Version
2 Fragmentation Denial of Service Vulnerability
24 March 2016
AusCERT Security Bulletin Summary
Product: Cisco IOS
Cisco IOS XE
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2016-1344
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Cisco Security Advisory
Cisco IOS and IOS XE Software Internet Key Exchange Version 2 Fragmentation
Denial of Service Vulnerability
Advisory ID: cisco-sa-20160323-ios-ikev2
Published: 2016 March 23 16:00 GMT
Version 1.0: Final
Base - 7.1
No workarounds available
Cisco Bug IDs:
A vulnerability in the Internet Key Exchange (IKE) version 2 (v2)
fragmentation code of Cisco IOS and IOS XE Software could allow an
unauthenticated, remote attacker to cause a reload of the affected system.
The vulnerability is due to an improper handling of crafted, fragmented IKEv2
packets. An attacker could exploit this vulnerability by sending crafted UDP
packets to the affected system. An exploit could allow the attacker to cause a
reload of the affected system.
Note: Only traffic directed to the affected system can be used to exploit this
vulnerability. This vulnerability can be triggered by IPv4 and IPv6 traffic.
Cisco has released software updates that address this vulnerability. This
advisory is available at the following link:
This advisory is part of the March 23, 2016, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes six Cisco
Security Advisories that describe six vulnerabilities. All the vulnerabilities
have a Security Impact Rating of "High." For a complete list of advisories and
links to them, see Cisco Event Response: Semiannual Cisco IOS and IOS XE
Software Security Advisory Bundled Publication.
This vulnerability affects products running a vulnerable version of Cisco IOS
or Cisco IOS XE Software. For more information about which Cisco IOS and IOS
XE Software releases are vulnerable, see the Fixed Software section of this
Devices running a vulnerable version of the software are affected if the
following two conditions are verified:
IKEv2 fragmentation is enabled
The device is running Cisco IOS or Cisco IOS XE Software and is configured for
any type of VPN based on IKEv2
Note: IKEv1-based VPNs are not affected by this vulnerability; however, in
some cases, enabling IKEv1 will automatically enable IKEv2.
A number of features use IKEv2, including different types of VPNs, such as the
Remote access VPN (excluding SSLVPN)
Dynamic Multipoint VPN (DMVPN)
Group Encrypted Transport VPN (GETVPN)
To verify whether IKEv2 fragmentation is enabled, use the show running-config
| include crypto ikev2 fragmentation command and verify that it returns
The following example shows a device running Cisco IOS Software with crypto
ikev2 fragmentation enabled:
router#show running-config | include crypto ikev2 fragmentation
crypto ikev2 fragmentation
Note: IKEv2 fragmentation is not enabled by default.
The preferred method to determine whether a device has been configured for
IKEv2 is to issue the show ip sockets or show udp EXEC command. If the device
has UDP port 500 or UDP port 4500 open, it is processing IKE packets.
In the following example, the device 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
Cisco IOS Software will also process IKE packets on UDP port 848 (GDOI), using
either IPv4 or IPv6, when the G-IKEv2 feature for GETVPN has been enabled.
Determining the Cisco IOS or Cisco IOS XE Software Version
To determine which Cisco IOS Software release is running on a Cisco product,
administrators can log in to the device, use the show version command in the
command-line interface, 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 image name appears 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 identifies a Cisco product that is running Cisco IOS
Software Release 15.5(2)T1 with an installed image name of
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 White Paper: Cisco IOS and NX-OS Software Reference
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this
IKEv2 fragmentation can be disabled by using the no crypto ikev2 fragmentation
If IKEv2 fragmentation is needed, there is no workaround that mitigates this
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:
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 consult the Cisco
Security Advisories and Responses archive at http://www.cisco.com/go/psirt and
review subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should ensure that the devices to upgrade 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 Technical Assistance Center (TAC):
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 menu 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
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
or IOS XE Software releasefor example, 15.1(4)M2 or 3.01.4Sin the following
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
Exploitation and Public Announcements
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.
This issue was found during an investigation of a related issue reported by
David Barksdale, Jordan Gruskovnjak, and Alex Wheeler of Exodus Intelligence.
Version Description Section Status Date
1.0 Initial public release. Final 2016-March-23
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS
LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO
CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information or
contain factual errors. The information in this document is intended for end
users of Cisco products.
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