Fetchmail versions 6.3.9 and below suffer from a NULL pointer deference vulnerability that can be triggered by outside circumstances.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/67408/fetchmail-SA-2007-02.txt
Source: https://packetstormsecurity.com/files/67408/fetchmail-SA-2007-02.txt.html