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CVE-2026-15305 — cms-form

Fix: TYPO3/typo3@817ad41

CVE-2026-15305 is a CWE-351 vulnerability in typo3/cms-form. A fix is available for typo3/cms-form — see the affected versions and patch details below.

TYPO3 CMS - Unrestricted File Upload in Form Framework

Also known asGHSA-mfqj-cqv3-h7xw
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-15305.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs16th percentile — riskier than 16% of all scored CVEsHighest risk
0.00%0.25%0.50%0.75%0.2%0.3%0.3%0.3%Aug 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected
🐘typo3/cms-form

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

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.

Solution

Update to TYPO3 version 14.3.5 LTS that fixes the problem described.

Credits

Thanks to Sébastien Convers for reporting this issue, and to Josua Vogel and Oliver Hader for fixing it.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagisttypo3/cms-form≥ 14.2.0&&< 14.3.514.3.5composer require typo3/cms-form:^14.3.5

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms-form, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update typo3/cms-form to 14.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-15305 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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. ### Solution Update to TYPO3 version 14.3.5 LTS that fixes the problem described. ### Credits Thanks to Sébastien Convers for reporting this issue, and
O3 Security · Impact-Aware SCA

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CVE-2026-15305: cms-form — Fixed in 14.3.5