CVE-2022-20837: A vulnerability in the DNS application layer gateway (ALG) functionality that is used by Network Address Translation (NAT) in Cisco IOS XE Software co...

Description

A vulnerability in the DNS application layer gateway (ALG) functionality that is 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 sending IPv4 TCP packets through an affected device. This vulnerability cannot be exploited by sending IPv6 traffic.

Metrics

CVSS 3.1

8.6/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Probability

0.87%

54.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cisco	Ios Xe	All versions

References

Timeline

Published: Oct 10, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-20837?

A vulnerability in the DNS application layer gateway (ALG) functionality that is 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 sending IPv4 TCP packets through an affected device. This vulnerability cannot be exploited by sending IPv6 traffic.

How severe is CVE-2022-20837?

CVE-2022-20837 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 0.87% probability of exploitation in the next 30 days.

How do I fix CVE-2022-20837?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.