CVE-2021-21357: Broken Access Control in Form Framework

Severity: high (CVSS 8.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-23 · updated 2026-06-17
Weakness: CWE-20

Description

TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 8.7.40, 9.5.25, 10.4.14, 11.1.1 due to improper input validation, attackers can by-pass restrictions of predefined options and submit arbitrary data in the Form Designer backend module of the Form Framework. In the default configuration of the Form Framework this allows attackers to explicitly allow arbitrary mime-types for file uploads - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. Besides that, attackers can persist those files in any writable directory of the corresponding TYPO3 installation. A valid backend user account with access to the form module is needed to exploit this vulnerability. This is fixed in versions 8.7.40, 9.5.25, 10.4.14, 11.1.1.

Affected products

typo3: from 8.0.0 before 8.7.40; from 9.0.0 before 9.5.25; from 10.0.0 before 10.4.14; from 11.0.0 before 11.1.1 — fixed in 10.4.14, 11.1.1, 8.7.40, 9.5.25

How to fix

Upgrade to a fixed version: typo3 10.4.14, 11.1.1, 8.7.40, 9.5.25. Check the vendor advisory for mitigations.

References

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