Vulnerability Alert

Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to bypass security restrictions on an affected system.

This vulnerability is due to an error within the Cisco IOS Software authentication proxy feature. An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious request to the affected system. If successful, the attacker could bypass proxy security protections and access protected resources.

Cisco has confirmed this vulnerability in a security advisory and released software updates.

Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.

To exploit this vulnerability, an attacker must have access to trusted, internal networks. Additionally, the attacker cannot exploit this vulnerability until another user establishes an active session with the targeted proxy. Because of a race condition, exploitation may not be reliable. The access requirements greatly limit the potential for exploitation.

An exploit could allow an attacker to bypass proxy security settings and access protected segments of the network. As a result, the attacker could make outgoing connections to external networks, potentially resulting in unauthorized data transmissions. The attacker could also access resources such as internal web services that are protected by a proxy server.

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

Cisco has released a security advisory to address Cisco bug ID CSCsy15227 at the following link: cisco-sa-20090923-auth-proxy