Executive Summary

This vulnerability exists in the TYPO3 CMS Form Framework where backend users with file write permissions can upload form definition files using mixed-case file extensions (such as .FORM.YAML) to bypass upload restrictions.

Because the system did not properly check file extensions in a case-insensitive manner, attackers could upload maliciously crafted form definition files that execute arbitrary SQL statements.

This allows attackers to escalate privileges by creating administrative backend user accounts, compromising the system's security.

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Impact Analysis

The vulnerability can lead to privilege escalation within TYPO3 CMS by allowing attackers to execute arbitrary SQL commands.

Specifically, attackers can create administrative backend user accounts, gaining full control over the CMS backend.

This can result in unauthorized access, modification, or deletion of content and configuration, potentially compromising the entire website or application.

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Detection Guidance

This vulnerability involves backend users uploading form definition files with mixed-case extensions (e.g., .FORM.YAML) to bypass upload restrictions. Detection involves identifying such suspicious files on your TYPO3 CMS installation.

You can scan your TYPO3 file storage or upload directories for files with mixed-case or unusual extensions related to form definitions, such as variations of .form.yaml with uppercase letters.

• Use a command to find files with mixed-case .form.yaml extensions, for example on a Linux system:
• find /path/to/typo3/uploads -type f -iname '*.form.yaml'
• Check backend user permissions to identify users with file write access who might upload such files.
• Review TYPO3 logs for unusual file upload activities or attempts to upload files with mixed-case extensions.

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Mitigation Strategies

The primary mitigation step is to update your TYPO3 CMS installation to a patched version that fixes this vulnerability.

• Upgrade to TYPO3 versions 10.4.57 ELTS, 11.5.51 ELTS, 12.4.46 ELTS, 13.4.31 LTS, or 14.3.3 LTS or later.
• Restrict backend user permissions to limit file write access only to trusted users.
• Follow TYPO3 Security Guide recommendations and subscribe to the typo3-announce mailing list for security updates.

These steps will prevent attackers from uploading malicious form definition files with mixed-case extensions and executing arbitrary SQL statements.

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