Title: Markus Kliegl mod_bf Buffer Overflow Vulnerability
Severity: MODERATE
Description:
mod_bf is an Apache module which allows execution of scripts written in the brainf*ck programming language. Brainf*ck is a language consisting of only eight commands. Noteably, it contains the ability to move through a byte array of memory, and display or modify values in this array.
The mod_bf interpreter does not impose boundary checking on the array allocated for the brainf*ck script. As a result, maliciously constructed scripts may overflow the allocated space, and read or modify arbitrary locations in memory. It may be possible to execute arbitrary code as the Apache process (generally user 'nobody').
If an administrator assumes that mod_bf presents a safe scripting enviroment, a local user may be able to exploit this to gain access to the nobody account. It is possible this could lead to further elevated privleges.
Normally, production web servers are configured to run as the user 'nobody'. This is an account with access to minimal server resources. This is designed to minimize the risks of a compromised web server.
Earlier versions of mod_bf may share this vulnerability.
Affected Products:
- Markus Kliegl mod_bf 0.2.0
References:
- Gobbles: ALERT! ALERT! REMOTE ACCESS VIA APACHE BRAINFUCKING! ALERT! ALERT!
- Markus Kliegl: mod_bf Homepage
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