Cisco IOS Software Internet Key Exchange Version 2 Anti-replay Protection Disabled Vulnerability

A vulnerability in the implementation of the Cisco IOS Software Internet Key Exchange version 2 (IKEv2) protocol may cause the anti-replay capabilities of IPsec to be disabled. This issue occurs only when using the Advanced Encryption Standard Galois/Counter Mode (AES-GCM) or the AES Galois Message Authentication Code (AES-GMAC) algorithms for Phase 2 IPsec Security Associations (SAs).

The vulnerability is due to improper coding of the logic required to enable or disable the anti-replay capabilities of an IPsec Phase 2 SA. An attacker could exploit this vulnerability by sending traffic that will traverse an IPsec tunnel. An exploit could allow the attacker to replay previously sent traffic as long as the application consuming the traffic does not implement its own sequence or anti-replay checks. Neither the confidentiality nor the authentication capabilities of IPsec are affected by this vulnerability.

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

Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.