High 7.5Known exploited (CISA KEV)Published Sep 28, 2017

CVE-2017-12231A 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 (D…

Updated under an hour ago (2026-10-19 08:40 UTC)

Does this affect you?

It affects cisco ios. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Mar 3, 2022; federal agencies had to remediate by Mar 24, 2022. Treat that date as your deadline.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for cisco ios

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-399
Known exploited: Added to CISA KEV Mar 3, 2022; federal remediation due Mar 24, 2022Apply updates per vendor instructions.
EPSS (exploitation in the next 30 days): 7.07% (percentile 94)
Assigned by: cisco
NVD analysis: Analyzed
Record last updated: Jan 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

cisco ios cisco:ios	from 12.4 through 15.6	NVD

References

http://www.securitytracker.com/id/1039449vdb-entry, x-refsource-sectrack, broken-link, third-party-advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-natx-refsource-confirm, vendor-advisory
http://www.securityfocus.com/bid/101039vdb-entry, x-refsource-bid, broken-link, third-party-advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12231us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.