Cisco IOS Software for Cisco Catalyst 6500 Series Switches and 7600 Series Routers ACL Bypass Vulnerability

A vulnerability in the ternary content addressable memory (TCAM) share access control list (ACL) functionality of Cisco IOS Software running on Supervisor Engine 720 and Supervisor Engine 32 Modules for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers could allow an unauthenticated, remote attacker to bypass access control entries (ACEs) in a port access control list (PACL).

The vulnerability is due to the improper implementation of PACL logic for ACEs that include a greater than operator, a less than operator, a tcp flag, the established keyword, or the range keyword. An attacker could exploit this vulnerability by sending packets that meet one or more filter criteria through an affected device. A successful exploit could allow the attacker to bypass the filters defined in the PACL for a targeted system.

Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

This advisory is available at the following link:

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161005-catalyst[“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161005-catalyst”]