CVE-2013-4206

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.

Published: 2013-08-19 Last update: 2026-04-29 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2013-4206 is rated Moderate Risk (53.1/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.14%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2013-4206

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 2.00% 1.14% -0.86%
2 2025-03-29 1.14% 2.00% +0.86%
3 2025-03-17 — 1.14% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2013-4206

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2013-4206

OS Trackers for CVE-2013-4206

vendor priority summary link
debian low CVE-2013-4206 low priority: Debian including 2 source packages (filezilla, putty), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 10. https://security-tracker.debian.org/tracker/CVE-2013-4206
gentoo normal CVE-2013-4206: 1 GLSA(s) (201309-08), 1 atom(s) (net-ftp/filezilla); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2013-4206
ubuntu medium CVE-2013-4206 medium priority: Ubuntu including 1 source packages (putty), 5 status rows across 5 suites (lucid, precise, quantal, raring, upstream): released 4, ignored 1. https://ubuntu.com/security/CVE-2013-4206

Affected software / configurations for CVE-2013-4206

Vendor Product Version Raw CPE
putty putty 0.45 cpe:2.3:a:putty:putty:0.45:*:*:*:*:*:*:*
putty putty 0.46 cpe:2.3:a:putty:putty:0.46:*:*:*:*:*:*:*
putty putty 0.47 cpe:2.3:a:putty:putty:0.47:*:*:*:*:*:*:*
putty putty 0.48 cpe:2.3:a:putty:putty:0.48:*:*:*:*:*:*:*
putty putty 0.49 cpe:2.3:a:putty:putty:0.49:*:*:*:*:*:*:*
putty putty 0.50 cpe:2.3:a:putty:putty:0.50:*:*:*:*:*:*:*
putty putty 0.51 cpe:2.3:a:putty:putty:0.51:*:*:*:*:*:*:*
putty putty 0.52 cpe:2.3:a:putty:putty:0.52:*:*:*:*:*:*:*
putty putty 0.53b cpe:2.3:a:putty:putty:0.53b:*:*:*:*:*:*:*
putty putty 0.54 cpe:2.3:a:putty:putty:0.54:*:*:*:*:*:*:*
putty putty 0.55 cpe:2.3:a:putty:putty:0.55:*:*:*:*:*:*:*
putty putty 0.56 cpe:2.3:a:putty:putty:0.56:*:*:*:*:*:*:*
putty putty 0.57 cpe:2.3:a:putty:putty:0.57:*:*:*:*:*:*:*
putty putty 0.58 cpe:2.3:a:putty:putty:0.58:*:*:*:*:*:*:*
putty putty 0.59 cpe:2.3:a:putty:putty:0.59:*:*:*:*:*:*:*
putty putty 0.60 cpe:2.3:a:putty:putty:0.60:*:*:*:*:*:*:*
putty putty 0.61 cpe:2.3:a:putty:putty:0.61:*:*:*:*:*:*:*
putty putty 2010-06-01 cpe:2.3:a:putty:putty:2010-06-01:r8967:*:*:development_snapshot:*:*:*
simon_tatham putty <= 0.62 cpe:2.3:a:simon_tatham:putty:*:*:*:*:*:*:*:*
simon_tatham putty 0.53 cpe:2.3:a:simon_tatham:putty:0.53:*:*:*:*:*:*:*

References for CVE-2013-4206

cvelogic Threat Intelligence