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Fencer Intel
medium 6.8

CVE-2013-4206 json

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 (…

published 13y ago modified 4mo ago also EUVD-2013-4111

cvss
6.8
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

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.

Patch / fix

  • putty Debian 14, Debian 13, Debian 12 0.63-1
  • filezilla Debian 14, Debian 13, Debian 12 3.7.3-1

debian advisories DEBIAN-CVE-2013-4206

  • filezilla openSUSE Tumbleweed 3.23.0.2-1.1

opensuse advisories openSUSE-SU-2024:10399-1

Is CVE-2013-4206 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2013-4206 updated cvss 7.5

putty: Integer overflow, leading to heap-based buffer overflow during SSH handshake

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.48% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.