Summary
TYPO3 CMS - Unrestricted File Upload in Form Framework
Problem
Users were able to upload files with arbitrary MIME types to forms using FileUpload or ImageUpload elements with allowedMimeTypes configured - uploading PHP files was not possible. The restriction was not enforced server-side because the MimeTypeValidator was registered during form building before concrete form definition properties were applied, resulting in the validator never being added to the processing pipeline.
Credits
Thanks to Sébastien Convers for reporting this issue, and to Josua Vogel and Oliver Hader for fixing it.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
Update to TYPO3 version 14.3.5 LTS that fixes the problem described.
Frequently Asked Questions
- What is CVE-2026-15305? CVE-2026-15305 is a medium-severity security vulnerability in typo3/cms-form (composer), affecting versions >= 14.2.0, <= 14.3.4. It is fixed in 14.3.5.
- Which versions of typo3/cms-form are affected by CVE-2026-15305? typo3/cms-form (composer) versions >= 14.2.0, <= 14.3.4 is affected.
- Is there a fix for CVE-2026-15305? Yes. CVE-2026-15305 is fixed in 14.3.5. Upgrade to this version or later.
- Is CVE-2026-15305 exploitable, and should I be worried? Whether CVE-2026-15305 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-15305 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-15305? Upgrade
typo3/cms-formto 14.3.5 or later.