What’s Vulnerable › Vulnerabilities

CVE-2026-104890: Kunstmaan CMS: MediaBundle extension blacklist bypass allows authenticated administrators to upload executable PHP files leading to remote code execution

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-05 · updated 2026-10-07
• Weakness: CWE-434

Description

Kunstmaan CMS is an open source content management system based on the Symfony framework. Prior to 7.3.2, src/Kunstmaan/MediaBundle/Helper/File/FileHandler.php performs the blacklisted_extensions check case-sensitively in FileHandler::getFilePath and lowercases the stored extension afterward. An authenticated backend user with media access can upload a mixed-case executable extension such as PHP that bypasses the check and is stored in the web-accessible media directory with an executable lowercase extension. The default blacklist also omits several server-executable extension types, allowing the same code-execution impact where the web server executes uploaded files. This issue is fixed in version 7.3.2.

Affected products

• kunstmaan bundles-cms: before 7.3.1
• KunstmaanBundlesCMS: before 7.3.1
• kunstmaan media-bundle: before 7.3.1

References

• https://github.com/Kunstmaan/KunstmaanBundlesCMS/commit/1bbdfdeac8e7e91506b1a9271360b9b68d7690d3
• https://github.com/Kunstmaan/KunstmaanBundlesCMS/releases/tag/7.3.2
• https://github.com/Kunstmaan/KunstmaanBundlesCMS/security/advisories/GHSA-p279-5wcv-45vq

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