CVE-2023-4255: W3m: out-of-bounds write in function checktype() in etc.c (incomplete fix for cve-2022-38223)

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-12-21 · updated 2026-06-17
Weakness: CWE-787

Description

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.

Affected products

Fedoraproject Extra Packages For Enterprise Linux: 8.0
Fedoraproject Fedora: 39
Tats W3M: 0.5.3+git20230121-1, 0.5.3+git20230121-2, 0.5.3+git20230129

References

https://bugzilla.redhat.com/show_bug.cgi?id=2255207
https://github.com/tats/w3m/commit/edc602651c506aeeb60544b55534dd1722a340d3
https://github.com/tats/w3m/issues/268
https://github.com/tats/w3m/pull/273
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/AULOBQJLXE2KCT5UVQMKGEFL4GFIAOED/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MKFZQUK7FPWWJQYICDZZ4YWIPUPQ2D3R/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TODROGVCWZ435HQIZE6ARQC5LPQLIA5C/
https://bugzilla.redhat.com/show_bug.cgi?id=2255207
https://github.com/tats/w3m/commit/edc602651c506aeeb60544b55534dd1722a340d3
https://github.com/tats/w3m/issues/268
https://github.com/tats/w3m/pull/273
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/AULOBQJLXE2KCT5UVQMKGEFL4GFIAOED/

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