Cisco Web Security Appliance HTTP Proxy Bypass Vulnerability

A vulnerability in the proxy engine of the Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to bypass the
security restriction.

The vulnerability is due to improper handling of malformed HTTP methods. An attacker could exploit this vulnerability by crafting an improper
HTTP method. An exploit could allow the attacker to circumvent the WSA’s ability to prevent proxied network traffic.

Cisco has confirmed the vulnerability in a security notice; however, software updates are not available.

To exploit this vulnerability, an attacker may need access to trusted, internal networks behind a firewall to send malformed HTTP methods to the targeted device. This access requirement may reduce the likelihood of a successful exploit.

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