man-cgi before 1.16 allows Local File Inclusion via absolute path traversal. If an Attacker provides a Filename as a Parameter (e.g. https://example.org/cgi-bin/man-cgi?/etc/passwd) the Script will read and return the local file. This is happening because of the way the Script calls the "man" command. Tests have shown that "man /some/random/file" (depending on it's configuration) will first try to locate a manual page for the given Parameter and will fallback to reading the file provided by the Parameter if it wasn't able to find the requested manual page.
The Author of the Script was contacted and was kind enough to provide a bugfix Version. You can find the bugfix Version here: http://users.softlab.ntua.gr/~christia/man-cgi.html
[Vendor of Product]
Panagiotis Christias (http://users.softlab.ntua.gr/~christia/)
[Affected Product Code Base]
man-cgi < 1.16
[Impact Information Disclosure]
[Has vendor confirmed or acknowledged the vulnerability?]