According to its self-reported version, the scanning engines of Cisco AsyncOS Software for Cisco Secure Web Appliance could allow an unauthenticated, remote attacker to bypass a configured rule, allowing traffic onto a network that should have been blocked. This vulnerability is due to improper detection of malicious traffic when the traffic is encoded with a specific content format. An attacker could exploit this vulnerability by using an affected device to connect to a malicious server and receiving crafted HTTP responses. A successful exploit could allow the attacker to bypass an explicit block rule and receive traffic that should have been rejected by the device.

This vulnerability affects Cisco Secure Web Appliance, both virtual and hardware versions, when the deflate, lzma, or brotli content-encoding type is enabled. The deflate content-encoding type is disabled by default, but the lzma and brotli content-encoding types are enabled by default.

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

Detections

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Cisco Secure Web Appliance Content Encoding Filter Bypass (cisco-sa-wsa-bypass-vXvqwzsj)

medium Nessus Plugin ID 181789

Version 1.0