Debian: DSA-2736-1: putty security update

    Date11 Aug 2013
    CategoryDebian
    31
    Posted ByLinuxSecurity Advisories
    Several vulnerabilities where discovered in PuTTY, a Telnet/SSH client for X. The Common Vulnerabilities and Exposures project identifies the following problems:
    
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    Debian Security Advisory DSA-2736-1                   This email address is being protected from spambots. You need JavaScript enabled to view it.
    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/
    
    Mailing list: This email address is being protected from spambots. You need JavaScript enabled to view it.
    
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