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.

Integer overflow in pcre_compile.c in Perl Compatible Regular Expressions (PCRE) before 6.2, as used in multiple products such as Python, Ethereal, and PHP, allows attackers to execute arbitrary code via quantifier values in regular expressions, which leads to a heap-based buffer overflow.