Perl-Compatible Regular Expression (PCRE) library before 6.7 allows context-dependent attackers to cause a denial of service (error or crash) via a regular expression that involves a "malformed POSIX character class", as demonstrated via an invalid character after a [[ sequence.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10985
https://bugzilla.redhat.com/show_bug.cgi?id=384761
http://www.securityfocus.com/bid/26725
http://www.redhat.com/support/errata/RHSA-2007-1068.html
http://www.redhat.com/support/errata/RHSA-2007-1059.html
http://www.pcre.org/changelog.txt
http://www.mandriva.com/security/advisories?name=MDVSA-2008:030
http://support.avaya.com/elmodocs2/security/ASA-2007-505.htm
http://secunia.com/advisories/28658
http://secunia.com/advisories/28041
http://lists.opensuse.org/opensuse-security-announce/2008-01/msg00006.html