TYPO3-EXT-SA-2026-001: Insecure Deserialization in extension "Mailqueue" (mailqueue)
It has been discovered that the extension "Mailqueue" (mailqueue) is vulnerable to insecure deserialization.
- Release Date: January 20, 2026
- Component Type: Third party extension. This extension is not a part of the TYPO3 default installation.
- Component: "Mailqueue" (mailqueue)
- Composer Package Name: cpsit/typo3-mailqueue
- Vulnerability Type: Insecure Deserialization
- Affected Versions: 0.5.0, 0.4.2 and below
- Severity: Medium
- Suggested CVSS v4.0: AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H
- References: CVE-2026-0895, CWE-502
Problem Description
The extension extends TYPO3’s FileSpool component, which was vulnerable to Insecure Deserialization prior to TYPO3-CORE-SA-2026-004. Since the related fix is overwritten by the extension, using the extension with a patched TYPO3 core version still allows for Insecure Deserialization, because the affected vulnerable code was extracted from TYPO3 core to the extension.
More information about this vulnerability can be found in the related TYPO3 Core Security Advisory TYPO3-CORE-SA-2026-004.
Solution
Updated versions 0.5.1 and 0.4.3 are available from the TYPO3 extension manager, packagist and at
https://extensions.typo3.org/extension/download/mailqueue/0.4.3/zip
https://extensions.typo3.org/extension/download/mailqueue/0.5.1/zip
Users of the extension are advised to update the extension as soon as possible.
Credits
Thanks to TYPO3 security team member Elias Häußler for reporting the vulnerability and for providing updated versions of the extension.
General Advice
Follow the recommendations that are given in the TYPO3 Security Guide. Please subscribe to the typo3-announce mailing list.