The FCGI (aka Fast CGI) module 0.70 through 0.73 for Perl, as used by CGI::Fast, uses environment variable values from one request during processing of a later request, which allows remote attackers to bypass authentication via crafted HTTP headers.
https://exchange.xforce.ibmcloud.com/vulnerabilities/69709
http://www.securityfocus.com/bid/49549
http://www.openwall.com/lists/oss-security/2011/09/08/2
http://www.openwall.com/lists/oss-security/2011/09/08/1
http://www.mandriva.com/security/advisories?name=MDVSA-2012:001