CVE-2026-15305: Typo3/cms form TYPO3 CMS - Unrestricted File Vulnerability

MODERATE
Advisory Identifier: GHSA-mfqj-cqv3-h7xw
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CWE-351
Published
Advisory Summary

CVE-2026-15305 is a MODERATE typo3 cms - unrestricted file vulnerability (CWE-351: Insufficient Type Distinction) affecting Typo3/cms form libraries in the Packagist ecosystem. The issue involves typo3 cms - unrestricted file upload in form framework. Remediation is available by upgrading affected packages to version 14.3.5.

CVE-2026-15305 at a Glance

CVE Identifier CVE-2026-15305
GHSA Identifier GHSA-mfqj-cqv3-h7xw
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-351: Insufficient Type Distinction
Affected Product Typo3/cms form
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-15305

To remediate this vulnerability, upgrade all affected Typo3/cms form dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

typo3/cms-form fixed: 14.3.5 
Upgrade typo3/cms-form to 14.3.5
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for typo3/cms-form

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-15305, inspect your project dependencies for Typo3/cms form:

inspect dependencies for typo3/cms-form

Analyze the terminal output to locate any version of Typo3/cms form in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 14.3.5), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-351: Insufficient Type Distinction, where the product does not properly distinguish between different types of elements in a way that leads to insecure behavior. In Typo3/cms form, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

CVE-2026-15305 Affected Typo3/cms form Versions

1 component(s)
Fixed Versions:
14.3.5
Product / Package Ecosystem Affected Versions Fixed Version
typo3/cms-form
 Packagist
≥ 14.2.0
< 14.3.5
14.3.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/TYPO3/typo3/security/advisories/GHSA-mfqj-cqv3-h7xw
NVD — CVE-2026-15305 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-15305
Security Fix Commit FIX COMMIT
https://github.com/TYPO3/typo3/commit/817ad41cc9dd28aac0fc4d0fe16fc25d46dd554a
Security Fix Commit FIX COMMIT
https://github.com/TYPO3/typo3/commit/cfda21050398eb145211a4fa6f9988f10e43e10b
Typo3/cms form Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms-form/CVE-2026-15305.yaml
Typo3/cms form Source Repository REPOSITORY
https://github.com/TYPO3/typo3
Typo3/cms form Security Information SECURITY
https://news.typo3.com/security/advisory/typo3-core-sa-2026-020
Typo3/cms form Security Information SECURITY
https://typo3.org/security/advisory/typo3-core-sa-2026-020

Frequently Asked Questions

What is CVE-2026-15305?
CVE-2026-15305 is a security vulnerability in Typo3/cms form involving TYPO3 CMS - Unrestricted File Upload in Form Framework under CWE-351: Insufficient Type Distinction.
Which Typo3/cms form versions are affected?
Affected versions include releases prior to 14.3.5 across affected packages: typo3/cms-form.
What version fixes CVE-2026-15305?
Upgrading to 14.3.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is typo3/cms-form affected?
Yes, typo3/cms-form is affected in releases prior to 14.3.5. Upgrade your dependency to 14.3.5 or later.
What CWE is associated with CVE-2026-15305?
CVE-2026-15305 is classified under CWE-351: Insufficient Type Distinction (The product does not properly distinguish between different types of elements in a way that leads to insecure behavior.).
How can I check Packagist dependencies for CVE-2026-15305?
Run the dependency tree command: 'inspect dependencies for typo3/cms-form'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mfqj-cqv3-h7xw",
  "modified" : "2026-08-31T19:53:59Z",
  "published" : "2026-08-31T19:53:59Z",
  "aliases" : [ "CVE-2026-15305" ],
  "summary" : "TYPO3 CMS - Unrestricted File Upload in Form Framework",
  "details" : "### Problem\nUsers 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.\n\n### Solution\nUpdate to TYPO3 version 14.3.5 LTS that fixes the problem described.\n\n### Credits\nThanks to Sébastien Convers for reporting this issue, and to Josua Vogel and Oliver Hader for fixing it.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "typo3/cms-form"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "14.2.0"
      }, {
        "fixed" : "14.3.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 14.3.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/TYPO3/typo3/security/advisories/GHSA-mfqj-cqv3-h7xw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-15305"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/TYPO3/typo3/commit/817ad41cc9dd28aac0fc4d0fe16fc25d46dd554a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/TYPO3/typo3/commit/cfda21050398eb145211a4fa6f9988f10e43e10b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms-form/CVE-2026-15305.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/TYPO3/typo3"
  }, {
    "type" : "WEB",
    "url" : "https://news.typo3.com/security/advisory/typo3-core-sa-2026-020"
  }, {
    "type" : "WEB",
    "url" : "https://typo3.org/security/advisory/typo3-core-sa-2026-020"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-351" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-31T19:53:59Z",
    "nvd_published_at" : null
  }
}