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AUSCERT External Security Bulletin Redistribution
ESB-2022.1606
Cisco IOS XE Software IPSec Denial of Service Vulnerability
14 April 2022
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE Software
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2022-20679
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-qfp-ipsec-GQmqvtqV
Comment: CVSS (Max): 6.8 CVE-2022-20679 (CVSS:3.1/AV:N/AC:H/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:H/PR:N/UI:N/S:C/C:N/I:N/A:H
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Cisco IOS XE Software IPSec Denial of Service Vulnerability
Priority: Medium
Advisory ID: cisco-sa-qfp-ipsec-GQmqvtqV
First Published: 2022 April 13 16:00 GMT
Version 1.0: Final
Workarounds: Yes
Cisco Bug IDs: CSCvz55575
CVE Names: CVE-2022-20679
CWEs: CWE-20
Summary
o A vulnerability in the IPSec decryption routine of Cisco IOS XE Software
could allow an unauthenticated, remote attacker to cause an affected device
to reload, resulting in a denial of service (DoS) condition.
This vulnerability is due to buffer exhaustion that occurs while traffic on
a configured IPsec tunnel is being processed. An attacker could exploit
this vulnerability by sending traffic to an affected device that has a
maximum transmission unit (MTU) of 1800 bytes or greater. A successful
exploit could allow the attacker to cause the device to reload.
To exploit this vulnerability, the attacker may need access to the trusted
network where the affected device is in order to send specific packets to
be processed by the device. All network devices between the attacker and
the affected device must support an MTU of 1800 bytes or greater. This
access requirement could limit the possibility of a successful exploit.
Cisco has released software updates that address this vulnerability. There
are workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-qfp-ipsec-GQmqvtqV
This advisory is part of the April 2022 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: April 2022
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication.
Affected Products
o Vulnerable Products
At the time of publication, this vulnerability affected the following Cisco
products if they were configured to terminate IPsec VPN connections and
were running a vulnerable release of Cisco IOS XE Software that was running
in autonomous or controller mode:
1000 Series Integrated Services Routers
4221 Integrated Services Routers
4321 Integrated Services Routers
4331 Integrated Services Routers
4351 Integrated Services Routers
Catalyst 8200 Series Edge Platform
Catalyst 8300 Series Edge Platform
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Device Configuration
A device that is running Cisco IOS XE Software is configured to terminate
IPsec VPN connections. If one of the following conditions match, the device
is affected:
A crypto map is configured for at least one interface
The device is configured with IPsec virtual tunnel interfaces (VTIs)
The MTU of the interface that is used for encryption must also be increased
to 1800 bytes or greater.
To determine whether a crypto map is configured for at least one interface,
use the show running-config | include ^interface|^ crypto map |^ mtu
command. The following example shows a crypto map named map-group1 and
increased MTU configured on the GigabitEthernet 0/0/0 interface:
Router# show running-config | include ^interface|^ crypto map |^ mtu
interface GigabitEthernet0/0/0
mtu 1800
crypto map map-group1
To determine whether the device is configured with IPsec VTIs, use the show
running-config | include ^interface|^ tunnel protection ipsec profile |^
mtu command and verify that the returned output contains tunnel protection
ipsec profile configured under at least one tunnel interface and that the
MTU has been increased on the physical interface associated to the tunnel.
The following example shows VTI interface Tunnel1 and increased MTU on
GigabitEthernet0/0/0:
Router# show running-config | include ^interface|^ tunnel protection ipsec profile |^ mtu
interface Tunnel1
tunnel protection ipsec profile vti-1
interface GigabitEthernet0/0/0
mtu 1800
Note : IPsec VPN is not configured by default.
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:
IOS Software
IOS XR Software
Meraki products
NX-OS Software
Workarounds
o There is a workaround that addresses this vulnerability. Lower the MTU to
less than 1800 bytes on all IPsec-enabled interfaces on affected devices by
using the following command:
Router(config-if)#mtu 1750
Note: This will require changing the MTU on all peers of the IPsec
connection.
While this workaround has been deployed and 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 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.
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 to identify
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 the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
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.
Related to This Advisory
o Cisco Event Response: April 2022 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-qfp-ipsec-GQmqvtqV
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2022-APR-13 |
+----------+---------------------------+----------+--------+--------------+
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