putty - several

Several vulnerabilities where discovered in PuTTY, a Telnet/SSH client
for X. The Common Vulnerabilities and Exposures project identifies the
following problems:

• CVE-2013-4206
  Mark Wooding discovered a heap-corrupting buffer underrun bug in the
  modmul function which performs modular multiplication. As the modmul
  function is called during validation of any DSA signature received
  by PuTTY, including during the initial key exchange phase, a
  malicious server could exploit this vulnerability before the client
  has received and verified a host key signature. An attack to this
  vulnerability can thus be performed by a man-in-the-middle between
  the SSH client and server, and the normal host key protections
  against man-in-the-middle attacks are bypassed.
• CVE-2013-4207
  It was discovered that non-coprime values in DSA signatures can
  cause a buffer overflow in the calculation code of modular inverses
  when verifying a DSA signature. Such a signature is invalid. This
  bug however applies to any DSA signature received by PuTTY,
  including during the initial key exchange phase and thus it can be
  exploited by a malicious server before the client has received and
  verified a host key signature.
• CVE-2013-4208
  It was discovered that private keys were left in memory after being
  used by PuTTY tools.
• CVE-2013-4852
  Gergely Eberhardt from SEARCH-LAB Ltd. discovered that PuTTY is
  vulnerable to an integer overflow leading to heap overflow during
  the SSH handshake before authentication due to improper bounds
  checking of the length parameter received from the SSH server. A
  remote attacker could use this vulnerability to mount a local denial
  of service attack by crashing the putty client.

Additionally this update backports some general proactive potentially
security-relevant tightening from upstream.

For the oldstable distribution (squeeze), these problems have been fixed in
version 0.60+2010-02-20-1+squeeze2. This update also provides a fix for
CVE-2011-4607, which was fixed for stable already.

For the stable distribution (wheezy), these problems have been fixed in
version 0.62-9+deb7u1.

For the unstable distribution (sid), these problems have been fixed in
version 0.63-1.

We recommend that you upgrade your putty packages.