Cms core: Duplicate Advisory: TYPO3-CORE-SA-2026-021: Broken Access Control in Backend and Install Tool
Description
A broken access control vulnerability exists in TYPO3 CMS backend and Install Tool due to ineffective referrer enforcement starting from version 13.0. This allows requests originating from any script running on the TYPO3 instance's own domains, such as frontend pages, to be accepted by backend and Install Tool endpoints. Attackers who can execute JavaScript on these domains, for example via cross-site scripting, could invoke these endpoints with the privileges of an authenticated user. The vulnerability affects TYPO3 CMS versions 13.0.0 through 13.4.33 and 14.0.0 through 14.3.5. A patch is available to address this issue.
CVSS v4.0
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The referrer enforcement mechanism introduced in TYPO3-CORE-SA-2020-006 (CVE-2020-11069) became ineffective starting with TYPO3 CMS version 13.0 due to a change in how backend and Install Tool applications are served—from a dedicated directory to the site's main entry script. This change caused the referrer check to compare against the site root, allowing any script running on the TYPO3 instance's own domains to be accepted by backend and Install Tool endpoints. Consequently, attackers able to execute JavaScript on these domains (e.g., via cross-site scripting) could perform requests to these sensitive endpoints with the privileges of an authenticated victim's session. The vulnerability affects versions 13.0.0 to 13.4.33 and 14.0.0 to 14.3.5 of TYPO3 CMS. A patch is available to fix this broken access control issue.
Potential Impact
An attacker who can execute JavaScript on a TYPO3 instance's domain can exploit this vulnerability to invoke backend and Install Tool endpoints with the privileges of an authenticated user. This could lead to unauthorized actions within the backend or installation tool, potentially compromising the integrity and security of the TYPO3 CMS installation. The vulnerability is classified as high severity.
Mitigation Recommendations
A patch is available for this vulnerability. Users should upgrade TYPO3 CMS to versions 13.4.34 or later and 14.3.6 or later to remediate the issue. Applying the official patch eliminates the broken access control risk. No additional mitigation steps are indicated by the vendor advisory.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-4f2f-jr2m-j7p4
- Osv Schema Version
- 1.4.0
- Ecosystems
- ["Packagist"]
- Database Specific Severity
- HIGH
- Cvss Version
- 4.0
Threat ID: 6a9845aeacd9273b496ae45a
Added to database: 09/02/2026, 15:50:06 UTC
Last enriched: 09/07/2026, 18:37:55 UTC
Last updated: 10/04/2026, 02:50:54 UTC
Views: 99
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