MEDIUM
The ParseValue function in lexer.c in tidy before 4.9.31 allows remote attackers to cause a denial of service (crash) via vectors involving multiple whitespace characters before an empty href, which triggers a large memory allocation.
http://lists.apple.com/archives/security-announce/2015/Sep/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Sep/msg00005.html
http://lists.apple.com/archives/security-announce/2015/Sep/msg00008.html
http://www.debian.org/security/2015/dsa-3309
http://www.openwall.com/lists/oss-security/2015/06/04/2
http://www.openwall.com/lists/oss-security/2015/07/13/7
http://www.openwall.com/lists/oss-security/2015/07/15/3
http://www.securityfocus.com/bid/75037
http://www.securitytracker.com/id/1033703
http://www.ubuntu.com/usn/USN-2695-1
https://github.com/htacg/tidy-html5/issues/217#issuecomment-108565501
https://support.apple.com/HT205212