The make_lockdir_name function in policy.c in pmount 0.9.18 allow local users to overwrite arbitrary files via a symlink attack on a file in /var/lock/.
http://security.debian.org/pool/updates/main/p/pmount/pmount_0.9.18-2+lenny1.diff.gz
http://www.debian.org/security/2010/dsa-2063