Posted at Debian: "
In SNS Advisory No. 32 a buffer overflow vulnerability has been reported in the routine which parses MIME headers that are returned from web servers. A
malicious web server administrator could exploit this and let the client web browser execute arbitrary code.
w3m handles MIME headers included in the request/response message of HTTP communication like any other web browser. A buffer overflow will be occur
when w3m receives a MIME encoded header with base64 format.
This problem has been fixed by the maintainer in version 0.1.10+0.1.11pre+kokb23-4 of w3m and w3m-ssl (for the SSL-enabled version), both for Debian
We recommend that you upgrade your w3m packages immediately."