An issue was discovered in the Tatsuya Kinoshita w3m fork before 0.5.3-31. w3m allows remote attackers to cause memory corruption in certain conditions via a crafted HTML page.
https://security.gentoo.org/glsa/201701-08
https://github.com/tats/w3m/commit/d43527cfa0dbb3ccefec4a6f7b32c1434739aa29
https://github.com/tats/w3m/blob/master/ChangeLog