Symptom
A vulnerability in the DNS application layer gateway (ALG) functionality used by Network Address Translation (NAT) in Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload.
This vulnerability is due to a logic error that occurs when an affected device inspects certain TCP DNS packets. An attacker could exploit this vulnerability by sending crafted DNS packets through the affected device that is performing NAT for DNS packets. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition on the affected device.
Note: This vulnerability can be exploited only by IPv4 TCP packets that are sent through an affected device. This vulnerability cannot be exploited by sending IPv6 traffic.
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-alg-dos-KU9Z8kFX
The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
Conditions
For information on fixed versions of software consult the Cisco IOS Software checker:
https://tools.cisco.com/security/center/softwarechecker.x
See Vulnerable Products Section of the advisory for full details:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-alg-dos-KU9Z8kFX#vp
Workaround
There are no workarounds that address this vulnerability.
Further Problem Description
Please refer to the Security Advisory.
PSIRT Evaluation
The Cisco PSIRT has assigned this bug the following CVSS version 3 score. The Base CVSS score as of the time of evaluation is 8.6:
https://tools.cisco.com/security/center/cvssCalculator.x?version=3.0&vector=CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CVE ID CVE-2022-20837 has been assigned to document this issue.
Additional information on Cisco's security vulnerability policy can be found at the following URL:
https://tools.cisco.com/security/center/resources/security_vulnerability_policy.html
