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FedoraOperating system · Fedoraproject

CVE-2023-4255

MEDIUM · 5.5 CVSS v3.1 Published 2023-12-21
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
58/100
Remediation priority · Elevated
Public exploit No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-787

The program writes past the bounds of a buffer, overwriting adjacent memory an attacker can turn to their advantage. Crafted input can overwrite control data and redirect execution. Remediation is validating every index and length before a write, plus modern memory-safety mitigations.

General guidance for the out-of-bounds write class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FedoraOperating system
Affected:= 39
W3mApplication
Affected:= 0.5.3\+git20230121-1= 0.5.3\+git20230121-2= 0.5.3\+git20230129
Extra Packages For Enterprise LinuxApplication
Affected:= 8.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Recommended fix Moderate confidence

Any w3m version after 0.5.3+git20230129 that includes the fix from commit edc602651c506aeeb60544b55534dd1722a340d3 (e.g., a version after January 2023 with the backspace handling fix in etc.c)

  1. Identify the current installed w3m version using: rpm -qa | grep w3m or dnf list installed w3m
  2. Check if your distribution has a newer package available that includes the security fix: dnf check-update or dnf update --info w3m
  3. If an updated package is available, apply the update: dnf update w3m
  4. If no updated package is available from your distribution, consider rebuilding w3m from source with the fix applied from commit edc602651c506aeeb60544b55534dd1722a340d3
  5. Verify the fix by testing with the specially crafted HTML file that triggered the vulnerability
  6. Confirm the updated version is running: w3m --version
Caveat Upgrading w3m to a newer version may introduce minor behavioral changes typical of version updates; review release notes for any breaking changes in the specific target version

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-4255 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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