CVE-2013-4206

medium

Published 2013-08-19 · Modified 2026-04-29

CVSS v3

—

CVSS v2

6.8

VIR risk

6.8

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.

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2013-4206

vendor Authored 2026-05-27

Vendor advisory: secalert@redhat.com — http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/vuln-modmul.html

vendor Authored 2026-05-27

Vendor advisory: secalert@redhat.com — http://svn.tartarus.org/sgt/putty/sshbn.c?sortby=date&r1=9977&r2=9976&pathrev=9977

vendor Authored 2026-05-27

Vendor advisory: secalert@redhat.com — http://secunia.com/advisories/54379

OS impact

OS	Version	Status	Fixed in
debian	bookworm	fixed	`3.7.3-1`
debian	bullseye	fixed	`3.7.3-1`
debian	forky	fixed	`3.7.3-1`
debian	sid	fixed	`3.7.3-1`
debian	trixie	fixed	`3.7.3-1`

Application impact

Vendor	Product	Versions
putty	putty	`0.45`
putty	putty	`0.46`
putty	putty	`0.47`
putty	putty	`0.48`
putty	putty	`0.49`
putty	putty	`0.50`
putty	putty	`0.51`
putty	putty	`0.52`
putty	putty	`0.53b`
putty	putty	`0.54`
putty	putty	`0.55`
putty	putty	`0.56`
putty	putty	`0.57`
putty	putty	`0.58`
putty	putty	`0.59`
putty	putty	`0.60`
putty	putty	`0.61`
putty	putty	`2010-06-01`
simon_tatham	putty	`{"endIncluding":"0.62"}`
simon_tatham	putty	`0.53`

References

CWEs

CWE-119

Verify integrity in audit chain (admin only). AS-IS.