TYPO3-EXT-SA-2026-005: Insecure Deserialization in extension "Mailqueue" (mailqueue)
It has been discovered that the extension "Mailqueue" (mailqueue) is vulnerable to insecure deserialization.
- Release Date: March 17, 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 - 0.5.1, 0.4.4 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-2026-1323, CWE-502
Problem Description
The extension fails to properly define allowed classes used when deserializing transport failure metadata. An attacker may exploit this to execute untrusted serialized code. Note that an active exploit requires write access to the directory configured at $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_spool_filepath'].
Solution
Updated versions 0.5.2 and 0.4.5 are available from the TYPO3 extension manager, packagist and at
https://extensions.typo3.org/extension/download/mailqueue/0.4.5/zip
https://extensions.typo3.org/extension/download/mailqueue/0.5.2/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.