It has been discovered that the Perl interpreter may encounter a buffer
overflow condition when compiling certain regular expressions containing
Unicode characters. This also happens if the offending characters are
contained in a variable reference protected by the \Q…\E quoting
construct. When encountering this condition, the Perl interpreter
typically crashes, but arbitrary code execution cannot be ruled out.
Read the full story: DSA-1556 perl – heap buffer overflow: http://www.debian.org/security/2008/dsa-1556