#VU42655 Buffer overflow in PuTTY - CVE-2013-4206

Vulnerability identifier: #VU42655

Vulnerability risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2013-4206

CWE-ID: CWE-119

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PuTTY
Client/Desktop applications / Software for system administration

Vendor: Simon Tatham

Description

The vulnerability allows a remote non-authenticated attacker to read and manipulate data.

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.

Mitigation
Install update from vendor's website.

Vulnerable software versions

PuTTY: 0.45 - 0.61

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

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.