TYPO3 CMS - Broken Access Control in Backend and Install Tool

Summary

The referrer enforcement introduced with TYPO3-CORE-SA-2020-006 (CVE-2020-11069) became ineffective in TYPO3 v13.0, where TYPO3 CMS started serving the backend and Install Tool applications from the site's main entry script instead of the dedicated typo3/ directory. Whether a request originated from the backend or Install Tool itself was determined by comparing the referrer against the directory of the entry script, which since then is the site root. As a consequence, requests originating from any script running on one of the TYPO3 instance's own domains, such as a frontend page, were accepted by backend routes and Install Tool endpoints. Attackers able to execute JavaScript on one of those domains, for instance by exploiting a cross-site scripting vulnerability, could invoke these endpoints via Fetch/XHR with the privileges of an authenticated victim's user session. This issue affects TYPO3 CMS versions 13.0.0-13.4.33 and 14.0.0-14.3.5.

Timeline

1. Aug 11, 2026, 7:29 AM UTCCVE published
2. Aug 11, 2026, 1:20 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Aug 11, 2026, 1:21 PM UTCRecord last updated

Affected versions

• typo3/cms-backend

  From 13.0.0 · fixed in 13.4.34; From 14.0.0 · fixed in 14.3.6

• typo3/cms-core

  From 13.0.0 · fixed in 13.4.34; From 14.0.0 · fixed in 14.3.6

• typo3/cms-install

  From 14.0.0 · fixed in 14.3.6

• typo3/cms-backendPackagist

  From 13.0.0 · fixed in 13.4.34

• typo3/cms-corePackagist

  From 14.0.0 · fixed in 14.3.6

References 5