Susam Pal has discovered a vulnerability in Apache, which can be exploited by malicious people to bypass certain security restrictions and disclose potentially sensitive information.

The vulnerability is caused due to a canonicalization error in the "mod_alias" module in the handling of case-sensitive alias directive arguments on file systems supporting case-insensitive directory names. This can e.g. be exploited to disclose the source code of applications placed in the "cgi-bin" directory on certain non-default configurations where the ScriptAlias directive references a directory inside the document root by accessing an URL with a capital directory name (e.g. "CGI-BIN").

Example of a vulnerable configuration:
DocumentRoot "[path]/docroot/"
ScriptAlias /cgi-bin/ "/[path]/docroot/cgi-bin"

NOTE: This only affects the Microsoft Windows platform.

The vulnerability has been confirmed in versions 2.0.59 and 2.2.3, and has also been reported in version 2.2.2. Other versions may also be affected.

Solution
Edit the configuration to ensure that alias directives (e.g. ScriptAlias) references directories outside of the document root.

Provided and/or discovered by
Susam Pal

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