Integer overflow in Perl-Compatible Regular Expression (PCRE) library before 6.7 allows context-dependent attackers to execute arbitrary code via a regular expression containing a large number of named subpatterns (name_count) or long subpattern names (max_name_size), which triggers a buffer overflow. NOTE: this issue was originally subsumed by CVE-2006-7224, but that CVE has been REJECTED and split.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2006-7227)