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Putty Security Update (SSH Tool)

Submitted by on August 20, 2013 – 4:33 PM
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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.
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