CVE-2011-3277: Unspecified vulnerability in the NAT implementation in Cisco IOS 12.1 through 12.4 and 15.0 through 15.1, a...

Security readout for executives and security teams

This CVE describes a remote denial-of-service risk in Cisco IOS and IOS XE NAT handling. A crafted H.323 packet sent to TCP port 1720 can force an affected device to reload, interrupting network availability. The source bundle does not provide CVSS, CWE, or detailed fixed-release information. Exposure is most likely on Cisco routing or switching devices running the listed IOS or IOS XE trains, with NAT enabled and TCP/1720 reachable from untrusted networks. Exact affected platforms and fixed versions require the Cisco advisory because the CVE data lacks CPEs. Treat this as a network availability issue for legacy Cisco infrastructure. It is important where affected NAT devices are exposed to H.323 traffic, but urgency should be driven by actual exposure because active exploitation is not evidenced in the provided sources. Mitigation focus: Review Cisco advisory for affected platforms and fixed software releases.; Upgrade affected IOS or IOS XE devices according to Cisco guidance.; Limit untrusted access to TCP/1720 where H.323 is not required..

Prepared

Jun 27, 2026, 17:48 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.