Cisco IOS XR Software Access Control List Bypass Vulnerability
A vulnerability in the hybrid access control list (ACL) processing of IPv4 packets in Cisco IOS XR Software could allow an unauthenticated, remote attacker to bypass a configured ACL.

This vulnerability is due to incorrect handling of packets when a specific configuration of the hybrid ACL exists. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass a configured ACL on the affected device.
For more information, see the  section of this advisory.
Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.