CVE-2021-21357: Broken Access Control in Form Framework
Problem 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.
Solution Update to TYPO3 versions 8.7.40, 9.5.25, 10.4.14, 11.1.1 that fix the problem described.
Credits Thanks to Richie Lee who reported this issue and to TYPO3 contributor Ralf Zimmermann who fixed the issue.
References TYPO3-CORE-SA-2021-003
Other sources
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.
— MITRE
TYPO3-CORE-SA-2021-003: Broken Access Control in Form Framework
Affected Software
Event History
Frequently Asked Questions
What is TYPO3-CORE-SA-2021-003?
TYPO3-CORE-SA-2021-003 is a vulnerability in the TYPO3 CMS that allows attackers to bypass restrictions and submit arbitrary data in the Form Designer backend module of the Form Framework.
What is the severity of CVE-2021-21357?
CVE-2021-21357 has a severity rating of 8.3, which is considered high.
How does CVE-2021-21357 affect TYPO3?
CVE-2021-21357 affects TYPO3 versions 8.7.40, 9.5.25, 10.4.14, and 11.1.1.
How can I fix TYPO3-CORE-SA-2021-003?
To fix TYPO3-CORE-SA-2021-003, upgrade to TYPO3 versions 8.7.41, 9.5.26, 10.4.15, or 11.1.2.
Where can I find more information about TYPO3-CORE-SA-2021-003?
You can find more information about TYPO3-CORE-SA-2021-003 in the TYPO3 security advisory TYPO3-CORE-SA-2021-003.