umount in util-linux 2.8 to 2.12q, 2.13-pre1, and 2.13-pre2, and other packages such as loop-aes-utils, allows local users with unmount permissions to gain privileges via the -r (remount) option, which causes the file system to be remounted with just the read-only flag, which effectively clears the nosuid, nodev, and other flags.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10921
https://exchange.xforce.ibmcloud.com/vulnerabilities/22241
http://www.ubuntu.com/usn/usn-184-1
http://www.securityfocus.com/bid/14816
http://www.securityfocus.com/archive/1/419774/100/0/threaded
http://www.novell.com/linux/security/advisories/2005_21_sr.html
http://www.debian.org/security/2005/dsa-825
http://www.debian.org/security/2005/dsa-823
http://support.avaya.com/elmodocs2/security/ASA-2006-014.htm
http://sunsolve.sun.com/search/document.do?assetkey=1-26-101960-1
http://secunia.com/advisories/18502
http://secunia.com/advisories/17154
http://secunia.com/advisories/17133
http://secunia.com/advisories/17027
http://secunia.com/advisories/17004
http://secunia.com/advisories/16988
http://secunia.com/advisories/16785