Summary
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.
Credits
Thanks to Hổ Cao Từ for reporting this issue, and to TYPO3 core & security team member Benjamin Franzke for fixing it.
Impact
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Update to TYPO3 versions 13.4.34 LTS, 14.3.6 LTS that fix the problem described.
Frequently Asked Questions
- What is CVE-2026-19418? CVE-2026-19418 is a high-severity cross-site request forgery (CSRF) vulnerability in typo3/cms-backend (composer), affecting versions >= 13.0.0, < 13.4.34. It is fixed in 13.4.34, 14.3.6. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- Which packages are affected by CVE-2026-19418?
typo3/cms-backend(composer) (versions >= 13.0.0, < 13.4.34)typo3/cms-core(composer) (versions >= 14.0.0, < 14.3.6)
- Is there a fix for CVE-2026-19418? Yes. CVE-2026-19418 is fixed in 13.4.34, 14.3.6. Upgrade to this version or later.
- Is CVE-2026-19418 exploitable, and should I be worried? Whether CVE-2026-19418 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-19418 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-19418?
- Upgrade
typo3/cms-backendto 13.4.34 or later - Upgrade
typo3/cms-coreto 14.3.6 or later
- Upgrade