CVE-2026-19418: TYPO3 CMS - Broken Access Control in Backend and Install Tool
Problem 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 Admin 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.
Solution Update to TYPO3 versions 13.4.34 LTS, 14.3.6 LTS that fix the problem described.
Credits Thanks to Hổ Cao Từ for reporting this issue, and to TYPO3 core & security team member Benjamin Franzke for fixing it.
Other sources
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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
composer/typo3/cms-coreto a version that resolves this vulnerability.Fixed in 14.3.6 - Upgrade
Upgrade
composer/typo3/cms-backendto a version that resolves this vulnerability.Fixed in 13.4.34 - Upgrade
Upgrade
TYPO3 CMSto a version that resolves this vulnerability.Fixed in 13.4.34 LTS - Upgrade
Upgrade
TYPO3 CMSto a version that resolves this vulnerability.Fixed in 14.3.6 LTS
Event History
Frequently Asked Questions
What is the severity of CVE-2026-19418?
CVE-2026-19418 has a severity score of 60, indicating a moderate risk level.
How do I fix CVE-2026-19418?
To fix CVE-2026-19418, upgrade to the latest version of TYPO3 CMS that addresses the broken access control issues.
What causes CVE-2026-19418 in TYPO3?
CVE-2026-19418 is caused by ineffective referrer enforcement in the TYPO3 backend and Install Tool applications.
What is the impact of CVE-2026-19418?
The impact of CVE-2026-19418 allows unauthorized access to the TYPO3 backend and Install Tool, potentially compromising the site.
Is CVE-2026-19418 related to previous vulnerabilities?
Yes, CVE-2026-19418 is related to CVE-2020-11069, where referrer enforcement was previously introduced but became ineffective.