Cisco IOS Software Network Address Translation Denial-of-Service Vulnerability

A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to the improper translation of H.323 messages that use the Registration, Admission, and Status (RAS) protocol and are sent to an affected device via IPv4 packets. An attacker could exploit this vulnerability by sending a crafted H.323 RAS packet through an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition. This vulnerability affects Cisco devices that are configured to use an application layer gateway with NAT (NAT ALG) for H.323 RAS messages. By default, a NAT ALG is enabled for H.323 RAS messages. Cisco Bug IDs: CSCvc57217.

Weakness: CWE-399

Patcharo shows this vulnerability for information but does not match versions for this product yet.

• n/a Cisco IOS · Cisco IOS

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat(opens in a new tab)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12231(opens in a new tab)

Cisco (CVE record)

Cisco (CVE record) · 27 Sept 2026, 23:46 UTC · Parser patcharo-cve5/1.1.0

CISA Known Exploited Vulnerabilities

CISA Known Exploited Vulnerabilities · 27 Sept 2026, 23:42 UTC · Parser patcharo-kev/1.0.0

NVD

NVD · 27 Sept 2026, 23:44 UTC · Parser patcharo-nvd/1.0.0

FIRST EPSS

FIRST EPSS · 27 Sept 2026, 23:46 UTC · Parser patcharo-epss/1.0.0

Last verified: 28 Sept 2026, 02:31 UTC