Cisco IOS XR Software Compression ACL Bypass Vulnerability

A vulnerability in the port or address range compression feature for access control lists (ACLs) on Typhoon line cards in Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device.

The vulnerability is due to incorrect port or address range encoding in the compression module of an ACL applied to an interface of an affected device. An attacker could exploit this vulnerability by sending traffic through an affected device that should otherwise be denied by the configured ACL. An exploit could allow the attacker to bypass protection offered by a configured ACL on an affected device.

Cisco has confirmed the vulnerability in a security notice and released software updates.

A successful exploit could allow an attacker to access trusted, internal networks that the targeted device is likely protecting. If the attacker gains access, the attacker could conduct further attacks.