Tavis Ormandy of the Google Security Team reported multiple pcre regular
expressions flaws.  Here are the details pasted from Tavis' mail:

CVE-2007-1660:
multiple forms of character class had their sizes miscalculated on
initial passes, resulting in too little memory being allocated, this
was also inadvertently fixed in version 7.0, where the compile phase
was entirely re-engineered (and much improved, from a security
standpoint).

Acknowledgements:

Red Hat would like to thank Tavis Ormandy and Will Drewry for properly disclosing these issues.