Perl-Compatible Regular Expression (PCRE) library before 7.0 does not properly calculate sizes for unspecified "multiple forms of character class", which triggers a buffer overflow that allows context-dependent attackers to cause a denial of service

Perl-Compatible Regular Expression (PCRE) library before 7.3 allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via regex patterns containing unmatched "\Q\E" sequences with orphan "\E" codes.