Title: Flicks Titan Application Firewall Escaped Character Decoding Vulnerability
Severity: CRITICAL
Description:
Titan Application Firewall is a firewall product designed to work with Microsoft's IIS webserver. It performs a variety of blocking functions, including the ability to check for patterns within a submitted HTTP request, and block the request if a suspect string is present.
Character encoding is used to escape problematic characters in URLs, by replacing them with a hexadecimal representation. For example, a & could be included in a request by replacing it with the character %26. This works for all characters, including those that would normally be directly represented.
Titan fails to decode these escaped characters when it does string matches on incoming HTTP requests. Thus, any pattern based rules in Titan may be trivially bypassed by an attacker replacing some characters in his string. For example, the string 'cmd.exe', commonly used to access a backdoor planted on a IIS server, may be replaced with the string 'cmd%2eexe'. While IIS will interpret both strings equally, Titan does not.
Affected Products:
- Flicks Software Titan 5.5.0a
References:
- Flicks Software: Titan Application Firewall
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