Mutt 1.5.19, when linked against (1) OpenSSL (mutt_ssl.c) or (2) GnuTLS (mutt_ssl_gnutls.c), allows connections when only one TLS certificate in the chain is accepted instead of verifying the entire chain, which allows remote attackers to spoof trusted servers via a man-in-the-middle attack.
Not vulnerable. This issue did not affect the versions of mutt as shipped with Red Hat Enterprise Linux 3, 4, or 5. Only mutt version 1.5.19 was affected by this flaw.