CVE-2026-19418: TYPO3 CMS - Broken Access Control in Backend and Install Tool

Severity: high (CVSS 7.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-11 · updated 2026-10-23
Weakness: CWE-346

Description

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.

Affected products

typo3: from 13.0.0 before 13.4.34; from 14.0.0 before 14.3.6 — fixed in 13.4.34, 14.3.6

How to fix

Upgrade to a fixed version: typo3 13.4.34, 14.3.6. Check the vendor advisory for mitigations.

References

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