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GHSA-9hq9-cr36-4wpj
No affected components available
Problem
By design, the file management module in TYPO3’s backend user interface has historically allowed the upload of any file type, with the exception of those that are directly executable in a web server context. This lack of restriction means it is possible to upload files that may be considered potentially harmful, such as executable binaries (e.g., .exe files), or files with inconsistent file extensions and MIME types (for example, a file incorrectly named with a .png extension but actually carrying the MIME type application/zip).
Although such files are not directly executable through the web server, their presence can introduce indirect risks. For example, third-party services such as antivirus scanners or malware detection systems might flag or block access to the website for end users if suspicious files are found. This could negatively affect the availability or reputation of the site.
Solution
Update to TYPO3 versions 9.5.51 ELTS, 10.4.50 ELTS, 11.5.44 ELTS, 12.4.31 LTS, 13.4.12 LTS that fix the problem described.
[!NOTE] The mitigation strategies outlined below apply broadly to all file uploads handled through TYPO3's File Abstraction Layer (FAL), not just those performed via the backend interface. This means that any extension or custom integration leveraging FAL will also be subject to the new validation rules and configuration options. Developers are advised to review the implications for their code and refer to the documentation of that change for guidance.
[!IMPORTANT]
Strong security defaults - Manual actions required
These versions introduce new configuration options to better control which files are permitted for upload and to improve consistency checks.
A new configuration option,
$GLOBALS['TYPO3_CONF_VARS']['SYS']['miscfile_ext'], has been added. This option allows administrators to explicitly define which file extensions should be permitted that are not already part of the built-in text or media file groups - examples include archive formats such asziporxz.In addition, two new feature flags have been introduced to enhance security:
security.system.enforceAllowedFileExtensions, enforces the defined list of allowed file extensions. This flag is enabled by default in new TYPO3 installations, but remains disabled in existing installations to prevent breaking changes.security.system.enforceFileExtensionMimeTypeConsistency, ensures that the uploaded file’s extension matches its actual MIME type, providing further validation of file integrity. This flag is active by default.It is recommended to configure the allowed file extensions via
$GLOBALS['TYPO3_CONF_VARS']['SYS']['miscfile_ext']and to enable the feature flagsecurity.system.enforceAllowedFileExtensionsto enforce the restriction.
Credits
Thanks to Hamed Kohi for reporting this issue, and to TYPO3 core & security team member Oliver Hader for fixing it.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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