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AUSCERT External Security Bulletin Redistribution
ESB-2024.1845
Cisco IOS and IOS XE Software Internet Key Exchange Version 1 Fragmentation
Denial of Service Vulnerabilities
28 March 2024
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS software
Cisco IOS XE Software
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2024-20307 CVE-2024-20308
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev1-NO2ccFWz
Comment: CVSS (Max): 8.6 CVE-2024-20308 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
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Cisco IOS and IOS XE Software Internet Key Exchange Version 1 Fragmentation
Denial of Service Vulnerabilities
Priority: High
Advisory ID: cisco-sa-ikev1-NO2ccFWz
First Published: 2024 March 27 16:00 GMT
Version 1.0: Final
Workarounds: Yes
Cisco Bug IDs: CSCwf11183 CSCwh66334
CVE Names: CVE-2024-20307 CVE-2024-20308
CWEs: CWE-121
Summary
o Multiple vulnerabilities in the Internet Key Exchange version 1 (IKEv1)
fragmentation feature of Cisco IOS Software and Cisco IOS XE Software could
allow an unauthenticated, remote attacker to cause a heap overflow or
corruption on an affected system.
For more information about these vulnerabilities, see the Details section
of this advisory.
Cisco has released software updates that address these vulnerabilities.
There are workarounds that address these vulnerabilities.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev1-NO2ccFWz
This advisory is part of the March 2024 release of the Cisco IOS and IOS XE
Software Security Advisory Bundled Publication. For a complete list of the
advisories and links to them, see Cisco Event Response: March 2024
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
These vulnerabilities affect Cisco products if they are running a
vulnerable release of Cisco IOS or IOS XE Software and both of the
following conditions are true:
IKEv1 fragmentation is enabled
Any type of VPN that is based on IKEv1 is configured
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
CVE-2024-20307: For this vulnerability to be exploited, the buffers huge
size command on the device must be configured for a value that is greater
than 32,767.
Determine the Configuration of IKEv1 Fragmentation
To determine whether IKEv1 fragmentation is enabled, use the show
running-config | include crypto isakmp fragmentation command. If the
command returns any output, IKEv1 fragmentation is enabled, as shown in the
following example:
router#show running-config | include crypto isakmp fragmentation
crypto isakmp fragmentation
Determine the Device IKEv1 Configuration
Features that use IKEv1 include different types of VPNs, such as the
following:
Dynamic Multipoint VPN (DMVPN)
FlexVPN
Group Encrypted Transport VPN (GET VPN)
LAN-to-LAN VPN
Remote access VPN (excluding SSLVPN)
The preferred method to determine whether a device has been configured for
IKEv1 is to use the show ip sockets or show udp EXEC command. If the device
has UDP port 500, UDP port 4500, or UDP port 848 (GDOI) open, it is
processing IKEv1 packets.
The following example shows the output of the show udp command on a device
that is processing IKEv1 packets on UDP port 500 and UDP port 4500, using
either IPv4 or 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#
Determine the Buffers Huge Configuration (Required for CVE-2024-20307 Only)
To determine if the buffers huge size has been altered from the default
value, use the show running-config | include buffers huge command and
verify that it returns output. If the command returns output and the value
of the buffers huge size is greater than 32,767, as shown in the following
example, the device is considered vulnerable:
router#show running-config | include buffers huge
buffers huge size 50000
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 the following
Cisco products:
Adaptive Security Appliance Software
Firepower Threat Defense Software
IOS XR Software
Meraki products
NX-OS Software
Details
o The vulnerabilities are not dependent on one another. Exploitation of one
of the vulnerabilities is not required to exploit the other vulnerability.
In addition, a software release that is affected by one of the
vulnerabilities may not be affected by the other vulnerability.
Details about the vulnerabilities are as follows:
CVE-2024-20308: Cisco IOS and IOS XE Software IKEv1 Fragmentation Heap
Underflow Denial of Service Vulnerability
A vulnerability in the IKEv1 fragmentation code of Cisco IOS Software and
Cisco IOS XE Software could allow an unauthenticated, remote attacker to
cause a heap underflow, resulting in an affected device reloading.
This vulnerability exists because crafted, fragmented IKEv1 packets are not
properly reassembled. An attacker could exploit this vulnerability by
sending crafted UDP packets to an affected system. A successful exploit
could allow the attacker to cause the affected device to reload, resulting
in a denial of service (DoS) condition.
Note: Only traffic that is 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. There
are workarounds that address this vulnerability.
Bug ID(s): CSCwh66334
CVE ID: CVE-2024-20308
Security Impact Rating (SIR): High
CVSS Base Score: 8.6
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CVE-2024-20307: Cisco IOS and IOS XE Software IKEv1 Fragmentation Heap
Overflow Denial of Service Vulnerability
A vulnerability in the IKEv1 fragmentation code of Cisco IOS Software and
Cisco IOS XE Software could allow an unauthenticated, remote attacker to
cause a heap overflow, resulting in an affected device reloading.
This vulnerability exists because crafted, fragmented IKEv1 packets are not
properly reassembled. An attacker could exploit this vulnerability by
sending crafted UDP packets to an affected system. A successful exploit
could allow the attacker to cause the affected device to reload, resulting
in a DoS condition.
Note: Only traffic that is 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. There
are workarounds that address this vulnerability.
Bug ID(s): CSCwf11183
CVE ID: CVE-2024-20307
Security Impact Rating (SIR): Medium
CVSS Base Score: 6.8
CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Workarounds
o CVE-2024-20308 : There is a workaround that addresses this vulnerability.
Disable IKEv1 fragmentation.
Use the commands in the following example to disable IKEv1 fragmentation:
Router# configure terminal
Router(config)#no crypto isakmp fragmentation
Router(config)#end
Router#
CVE-2024-20307 : There are workarounds that address this vulnerability.
Either revert the buffers huge configuration to its default value or
disable IKEv1 fragmentation.
Use the commands in the following example to revert the buffers huge
configuration to its default value:
Router# configure terminal
Router(config)#default buffers huge size
Router(config)#end
Router#
Use the commands in the following example to disable IKEv1 fragmentation:
Router# configure terminal
Router(config)#no crypto isakmp fragmentation
Router(config)#end
Router#
The IKE v1 fragmentation feature provides for the fragmentation of large
IKE packets into a series of smaller IKE packets to avoid fragmentation at
the UDP layer (for example, for large certificate payloads or certificate
request payloads). Some third-party vendor devices, such as firewalls that
are configured for stateful packet inspection, do not permit the
passthrough of UDP fragments in case they are part of a fragmentation
attack.
While these workarounds have been deployed and were proven successful in a
test environment, customers should determine the applicability and
effectiveness in their own environment and under their own use conditions.
Customers should be aware that any workaround or mitigation that is
implemented may negatively impact the functionality or performance of their
network based on intrinsic customer deployment scenarios and limitations.
Customers should not deploy any workarounds or mitigations before first
evaluating the applicability to their own environment and any impact to
such environment.
Fixed Software
o Cisco has released free software updates that address the vulnerabilities
described in this advisory. Customers with service contracts that entitle
them to regular software updates should obtain security fixes through their
usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information
about licensing and downloads. This page can also display customer device
support coverage for customers who use the My Devices tool.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories 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 . This tool
identifies any Cisco security advisories that impact a specific software
release and the earliest release that fixes the vulnerabilities that are
described in each advisory ("First Fixed"). If applicable, the tool also
returns the earliest release that fixes all the vulnerabilities that are
described in all the advisories that the Software Checker identifies
("Combined First Fixed").
To use the tool, go to the Cisco Software Checker page and follow the
instructions. Alternatively, use the following form to determine whether a
release is affected by any Cisco Security Advisory. To use the form, follow
these steps:
1. Choose which advisories the tool will search-only this advisory, only
advisories with a Critical or High Security Impact Rating (SIR) , or
all advisories.
2. Enter a release number-for example, 15.9(3)M2 or 17.3.3.
3. Click Check .
[2 ] [ ] [Critical,High,Medium]
[Only this advisory ]
[ ] [Check]
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 CVE-2024-20307 was found during internal security testing by X. B. of the
Cisco Advanced Security Initiatives Group (ASIG).
CVE-2024-20308 was found during internal security testing by the Cisco
Advanced Security Initiatives Group (ASIG).
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 2024 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ikev1-NO2ccFWz
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2024-MAR-27 |
+----------+---------------------------+----------+--------+--------------+
Legal Disclaimer
o 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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