CVE-2011-3277: Cisco IOS

High severity, CVSS 7.8. EPSS: 1.8% chance of exploitation in the next 30 days.

Unspecified vulnerability in the NAT implementation in Cisco IOS 12.1 through 12.4 and 15.0 through 15.1, and IOS XE 3.1.xSG, allows remote attackers to cause a denial of service (device reload) by sending crafted H.323 packets to TCP port 1720, aka Bug ID CSCth11006.

Affected products

• Cisco IOS: version 12.1 only; version 12.1e only; version 12.2 only; version 12.2b only; version 12.2bc only; version 12.2bx only; …
• Cisco IOS XE: version 3.1.0sg only; version 3.1.1sg only

Published 2011-10-03. Last modified 2026-06-16.