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Fencer Vulns
medium 5.5

CVE-2023-4255 json

W3m: out-of-bounds write in function checktype() in etc.c (incomplete fix for cve-2022-38223)

published 2023-12-21 2 y ago modified 2026-06-17 4 mo ago also EUVD-2023-54126

cvss
5.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

An out-of-bounds write issue has been discovered in the backspace handling of the checkType() function in etc.c within the W3M application. This vulnerability is triggered by supplying a specially crafted HTML file to the w3m binary. Exploitation of this flaw could lead to application crashes, resulting in a denial of service condition.

Patch / fix

  • w3m Debian 14, Debian 13 0.5.3+git20230121-2.1

debian advisories DEBIAN-CVE-2023-4255

  • w3m Ubuntu 20.04 LTS 0.5.3-37ubuntu0.2
  • w3m Ubuntu 22.04 LTS 0.5.3+git20210102-6ubuntu0.2
  • w3m Ubuntu 24.04 LTS 0.5.3+git20230121-2ubuntu1
  • w3m Ubuntu Pro 14.04 LTS 0.5.3-15ubuntu0.2+esm2
  • w3m Ubuntu Pro 18.04 LTS 0.5.3-36ubuntu0.1+esm1

ubuntu advisories UBUNTU-CVE-2023-4255

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • w3m SLES for SAP 12 SP5, SLES 12 SP5 0.5.3.git20161120-161.9.1

suse advisories SUSE-SU-2024:0014-1

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-2023-4255 updated cvss 5.5

w3m: out-of-bounds write in function checkType() in etc.c (incomplete fix for CVE-2022-38223)

  • 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

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/tats/w3m/issues/268 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected products

  • n/a w3m
  • Fedora Fedora
  • Fedora Extra Packages for Enterprise Linux

Classification

Weakness

References

Sources

Fencer Vulns 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.