Vulnerability Instance

Gaëtan Leurent informed us of a weakness in APOP
authentication that could allow an attacker to recover the first
part of your mail password if the attacker could interpose
a malicious mail server on your network masquerading as your legitimate
mail server. With normal settings it could take several hours for
the attacker to gather enough data to recover just a few characters
of the password. This result was presented at the
Fast Software Encryption 2007 conference.In a rump session at the same conference a team from The University of
Electro-Communications claimed that a variant on the same hash-collision
attack allowed them to recover a 31 character password.Fixed versions of Thunderbird and SeaMonkey mail prevent this
technique by stricter enforcement of the Message-ID format used
by APOP.POP mail accounts which do not use any authentication are
common and in the same hypothetical situation the password could
be recovered immediately without any special programming on the
attacker's part.