CVE-2013-4206

Severity: medium (CVSS 6.8 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2013-08-19 · updated 2026-06-16
Weakness: CWE-119

Description

Heap-based buffer underflow in the modmul function in sshbn.c in PuTTY before 0.63 allows remote SSH servers to cause a denial of service (crash) and possibly trigger memory corruption or code execution via a crafted DSA signature, which is not properly handled when performing certain bit-shifting operations during modular multiplication.

Affected products

PuTTY: 0.45, 0.46, 0.47, 0.48, 0.49, 0.50 (+12)
Simon Tatham Putty: through 0.62; 0.53

References

http://lists.opensuse.org/opensuse-updates/2013-08/msg00035.html
http://secunia.com/advisories/54379
http://secunia.com/advisories/54533
http://svn.tartarus.org/sgt/putty/sshbn.c?sortby=date&r1=9977&r2=9976&pathrev=9977
http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/vuln-modmul.html
http://www.debian.org/security/2013/dsa-2736
http://www.openwall.com/lists/oss-security/2013/08/06/11
http://lists.opensuse.org/opensuse-updates/2013-08/msg00035.html
http://secunia.com/advisories/54379
http://secunia.com/advisories/54533
http://svn.tartarus.org/sgt/putty/sshbn.c?sortby=date&r1=9977&r2=9976&pathrev=9977
http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/vuln-modmul.html

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