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CVE-2026-77143 – Broken Access Control / Unauthorized Content Modification – TYPO3 Forum Extension (

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Summary

CVE-2026-77143 is a broken access control vulnerability in the TYPO3 third-party extension "Forum" (jweiland/pforum) that allows an unauthenticated visitor to overwrite the content of any forum topic. The extension fails to verify server-side that the requester owns the topic being edited, and because topic identifiers are publicly visible in the forum listing, exploitation requires no authentication or special access. The issue carries a CVSS score of 8.8 (High).

Technical details

  • Root cause: The frontend topic-editing flow in the pforum extension does not perform a server-side ownership check before applying an update to a topic.
  • Trigger conditions: An attacker needs only the numeric identifier of an existing public forum topic, which is exposed in the normal topic listing.
  • Attack vector: Network — the attacker submits a direct, modified update request (POST) referencing the target topic ID, without needing to authenticate or hold any privilege on the site.
  • Impact: Unauthorized modification/overwrite of forum topic content, affecting data integrity of the forum; no confidentiality or availability impact beyond content tampering is described in the advisory.

Affected software

  • TYPO3 extension "Forum" (pforum): versions 4.0.3 and below
  • TYPO3 extension "Forum" (pforum): version 5.0.0
  • TYPO3 extension "Forum" (pforum): versions 6.0.0 through 6.2.3

Severity

  • CVSS v4.0 Base Score: 8.8 (High)
  • Vector: AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Update the pforum extension to the fixed versions: 4.0.4, 5.0.1, or 6.2.4, via the TYPO3 extension manager, Packagist, or the extensions.typo3.org download page.
  • If no patch can be applied immediately: Restrict or disable public frontend topic-editing functionality in the forum extension configuration, and monitor forum content for unauthorized changes until the update is applied.

References

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