DSA 2736-1: putty security update
Posted on: 08/12/2013 08:27 AM

A putty security update has been released for Debian GNU/Linux

DSA 2736-1: putty security update


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Debian Security Advisory DSA-2736-1 security@debian.org
http://www.debian.org/security/ Salvatore Bonaccorso
August 11, 2013 http://www.debian.org/security/faq
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Package : putty
Vulnerability : several
Problem type : local (remote)
Debian-specific: no
CVE ID : CVE-2013-4206 CVE-2013-4207 CVE-2013-4208 CVE-2013-4852
Debian Bug : 718779

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.

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: http://www.debian.org/security/



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