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CVE-2026-77140 – Unauthenticated Record Tampering (Broken Access Control) – TYPO3 “Telephone Directo

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Summary

CVE-2026-77140 is a broken access control vulnerability in the TYPO3 "Telephone Directory" extension (Composer package jweiland/telephonedirectory) that allows an unauthenticated attacker to overwrite employee directory records. The extension validates an HMAC token on the frontend edit link only when the edit form is rendered, but not when the update is actually persisted, allowing the authorization check to be bypassed entirely. The issue carries a CVSS v4.0 base score of 8.7 (High), driven by network exploitability, no privileges/user interaction required, and high impact on data integrity.

Technical details

  • Root cause: The extension performs HMAC signature validation on the frontend "edit employee" link only in the controller action that renders the edit form. The action that actually persists (saves) the submitted change does not re-validate the HMAC, so the integrity/authorization check can be skipped entirely.
  • Trigger condition: An attacker only needs to know (or guess/enumerate) the UID of a visible employee record in the public-facing telephone directory.
  • Attack vector: The attacker crafts and sends a direct HTTP POST request to the update action of the extension, bypassing the normal flow of requesting a signed edit link first.
  • Impact: Unauthenticated modification (overwrite) of employee directory records — a violation of data integrity. No authentication, prior privileges, or user interaction are required to exploit the flaw.
  • Weakness classification: CWE-862 (Missing Authorization) and CWE-639 (Authorization Bypass Through User-Controlled Key).

Affected software

  • TYPO3 Extension "Telephone Directory" (jweiland/telephonedirectory), all versions 6.1.2 and below.

Severity

  • CVSS v4.0 Base Score: 8.7 (High)
  • Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade the "Telephone Directory" extension to version 6.2.0 or later via the TYPO3 extension manager, Packagist, or the official repository, where the update action now correctly re-validates the HMAC signature before persisting changes.
  • If immediate patching is not possible:
    • Restrict or disable public-facing frontend edit functionality for the telephone directory plugin until the update can be applied.
    • Use a web application firewall or reverse proxy rule to block direct POST requests to the extension’s update/edit endpoints from unauthenticated sources.
    • Monitor telephone directory records for unexpected/unauthorized modifications as a compensating detective control.

References

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