Multiple format string vulnerabilities in mcrypt 2.6.8 and earlier might allow user-assisted remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via vectors involving (1) errors.c or (2) mcrypt.c.
http://www.securityfocus.com/bid/55557
http://www.openwall.com/lists/oss-security/2012/09/13/22
http://www.openwall.com/lists/oss-security/2012/09/10/5