CVE-2021-21355 Unrestricted File Upload in Form Framework

What is CVE-2021-21355?

CVE-2021-21355 is a high-severity vulnerability in Typo3 Typo3, published on 23 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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 the lack of ensuring file extensions belong to configured allowed mime-types, attackers can upload arbitrary data with arbitrary file extensions - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. Besides that, _UploadedFileReferenceConverter_ transforming uploaded files into proper FileReference domain model objects handles possible file uploads for other extensions as well - given those extensions use the Extbase MVC framework, make use of FileReference items in their direct or inherited domain model definitions and did not implement their own type converter. In case this scenario applies, _UploadedFileReferenceConverter_ accepts any file mime-type and persists files in the default location. In any way, uploaded files are placed in the default location _/fileadmin/user_upload/_, in most scenarios keeping the submitted filename - which allows attackers to directly reference files, or even correctly guess filenames used by other individuals, disclosing this information. No authentication is required to exploit this vulnerability. This is fixed in versions 8.7.40, 9.5.25, 10.4.14, 11.1.1.

Weakness: CWE-552, CWE-434

Which versions are affected by CVE-2021-21355?

21 open source packages ship an affected version, including typo3/cms-form, typo3 and typo3/cms. It affects 1 product.

Products include Typo3 Typo3.

How do I fix CVE-2021-21355?

Upgrade typo3/cms-form to a fixed version for your release line: 10.4.14, 11.1.1, 8.7.40 or 9.5.25.

Is CVE-2021-21355 being exploited?

There is no known exploitation of CVE-2021-21355 in the wild and no public exploit code.

Other vulnerabilities in Typo3 Typo3

• CVE-2009-0258 Indexed Search Engine for TYPO3 Command Execution via Metacharacter Injection Critical 10.0
• CVE-2011-3583 Typo3 SQL injection due to faulty prepared statements Critical 9.8
• CVE-2011-4628 Typo3 Authentication Bypass Critical 9.8
• CVE-2023-24814 Persisted Cross-Site Scripting in Frontend Rendering in typo3 High 8.8
• CVE-2021-41113 Cross-Site-Request-Forgery in Backend URI Handling in Typo3 High 8.8

All Typo3 Typo3 vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-typo3-2021-21355, GHSA-2r6j-862c-m2v2.