source: https://www.securityfocus.com/bid/305/info

The man command created a temporary file under /tmp with a predictable name and is willing to follow symbolic links. This may allow malicious local users to create arbitrarily named files.

zsoelim(1) is a utility part of the man package which prepocess man pages and satisfy .so requests in roff input. This utility may be called when running the man(1) command. It creates temporary filenames are of the form "/tmp/zman0<pid>aaa" where <pid> is the process id of the zsoelim process. The program fails to check for the existance of symlinks and follows them creating arbitrary files with the permissions of the user running man. 

perl -e 'for($i=1000;$i<5000;$i++){symlink "/etc/nologin", "/tmp/zman0${i}aaa";}'