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Date: Tue, 6 Jan 2009 14:46:46 -0500 (EST)
From: Josh Bressers <>
To: oss-security <>
Subject: Fwd: Using xdg-open in /etc/mailcap causes hole in Firefox
 (Demonstration/Exploit included)

Here's a heads up for everyone (I've CCd the discoverer)

Steve, can you assign a CVE id.


----- Forwarded Message -----


as I've seen, you also seem to use xdg-open in /etc/mailcap.

The problem is, that xdg-open, itself, detects the right mime-type. This allowes an attacker to deliver a dangerous file with a trustworthy mime-type to get it executed by xdg-open.

I've created an example page: (With SSL) (Without SSL)

This page delivers a .desktop file with the mime-type "application/pdf". In default configuration, Firefox offers to open this file with the default application, which is xdg-open. Just one click on "OK" (and most users won't have a closer look at the dialog!) and the content in the .desktop file is immediately executed!

Other combinations are possible, I just got the first result with .desktop files. There may be other dangerous types, Firefox may be tricked to open with xdg-open. It's even possible to hide the real file type.

See also:
Problem: Their security bugs are open to the public :-( Fast reaction would be required :-(


Manuel Reimer
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