gnutls26 - security update

Karthikeyan Bhargavan and Gaetan Leurent at INRIA discovered a flaw in
the TLS 1.2 protocol which could allow the MD5 hash function to be used
for signing ServerKeyExchange and Client Authentication packets during a
TLS handshake. A man-in-the-middle attacker could exploit this flaw to
conduct collision attacks to impersonate a TLS server or an
authenticated TLS client.

More information can be found at

https://www.mitls.org/pages/attacks/SLOTH

For the oldstable distribution (wheezy), this problem has been fixed
in version 2.12.20-8+deb7u5.

We recommend that you upgrade your gnutls26 packages.