Vulnerability record · CVE-2013-4206 · published 19 August 2013

CVE-2013-4206: Putty memory buffer overflow vulnerability

Putty · Putty

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.

6.8 CVSS 2.0 Medium EPSS 2.5% · top 16.1% CWE-119 · Memory buffer overflow

6.8CVSS 2.0 base score

2.5%EPSS exploitation probability, 30 days

NoNot in CISA KEV

2Affected product versions listed by NVD

14References

16 Jun 2026Last modified by NVD

Description

AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Putty Putty SPutty Simon Tatham

References

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

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2004-1008Putty vulnerabilityInteger signedness error in the ssh2_rdpkt function in PuTTY before 0.56 allows remote attackers to execute arbitrary code via a SSH2_MSG_DEBUG packe…EPSS 7.4%10 Jan 2005 10.0CVE-2002-1357Cisco ios memory buffer overflow vulnerabilityMultiple SSH2 servers and clients do not properly handle packets or data elements with incorrect length specifiers, which may allow remote attackers …EPSS 9.8%23 Dec 2002 10.0CVE-2002-1358Cisco ios improper input validation vulnerabilityMultiple SSH2 servers and clients do not properly handle lists with empty elements or strings, which may allow remote attackers to cause a denial of …EPSS 5.8%23 Dec 2002 10.0CVE-2002-1359SSH2 implementations mishandle large packets, enabling DoS and possible code executionMultiple SSH2 servers and clients fail to properly handle large packets or large fields, leading to buffer overflow conditions. The flaw was demonstr…EPSS 80%analysed23 Dec 2002 10.0CVE-2002-1360Cisco ios improper input validation vulnerabilityMultiple SSH2 servers and clients do not properly handle strings with null characters in them when the string length is specified by a length field, …EPSS 6.1%23 Dec 2002 9.8CVE-2019-17067Putty allocation without limits vulnerabilityPuTTY before 0.73 on Windows improperly opens port-forwarding listening sockets, which allows attackers to listen on the same port to steal an incomi…EPSS 1.6%1 Oct 2019 9.8CVE-2019-9895Putty memory buffer overflow vulnerabilityIn PuTTY versions before 0.71 on Unix, a remotely triggerable buffer overflow exists in any kind of server-to-client forwarding.EPSS 2.6%21 Mar 2019 9.8CVE-2019-9898Putty vulnerabilityPotential recycling of random numbers used in cryptography exists within PuTTY before 0.71.EPSS 3.9%21 Mar 2019

Source: NIST National Vulnerability Database (record CVE-2013-4206), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.