shorewall 1.4.10c and earlier, and 2.0.x before 2.0.3a, allows local users to overwrite arbitrary files via a symlink attack on the chains-$$ temporary file.
https://exchange.xforce.ibmcloud.com/vulnerabilities/16651
http://www.mandrakesecure.net/en/advisories/advisory.php?name=MDKSA-2004:080
http://www.gentoo.org/security/en/glsa/glsa-200407-07.xml
http://lists.shorewall.net/pipermail/shorewall-announce/2004-June/000385.html