CVE-2026-0859: TYPO3 CMS Allows Insecure Deserialization via Mailer File Spool
Problem Local platform users who can write to TYPO3’s mail‑file spool directory can craft a file that the system will automatically deserialize without any class restrictions. This flaw allows an attacker to inject and execute arbitrary PHP code in the public scope of the web server.
The vulnerability is triggered when TYPO3 is configured with $GLOBALS['TYPO3CONFVARS']['MAIL']['transportspooltype'] = 'file'; and a scheduler task or cron job runs the command mailer:spool:send. The spool‑send operation performs the insecure deserialization that is at the core of this issue.
Solution Update to TYPO3 versions 10.4.55 ELTS, 11.5.49 ELTS, 12.4.41 LTS, 13.4.23 LTS, 14.0.2 that fix the problem described.
Credits Thanks to Vitaly Simonovich for reporting this issue, and to TYPO3 security team members Elias Häußler and Oliver Hader for fixing it.
References TYPO3-CORE-SA-2026-004
Other sources
TYPO3's mail‑file spool deserialization flaw lets local users with write access to the spool directory craft a malicious file that is deserialized during the mailer:spool:send command, enabling arbitrary PHP code execution on the web server. This issue affects TYPO3 CMS versions 10.0.0-10.4.54, 11.0.0-11.5.48, 12.0.0-12.4.40, 13.0.0-13.4.22 and 14.0.0-14.0.1.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-0859?
CVE-2026-0859 is classified as a critical vulnerability due to its ability to enable arbitrary PHP code execution.
How do I fix CVE-2026-0859?
To mitigate CVE-2026-0859, users should upgrade to TYPO3 versions 10.4.55 and above, 11.5.49 and above, 12.4.41 and above, 13.4.23 and above, or 14.0.2 and above.
Who is affected by CVE-2026-0859?
CVE-2026-0859 affects TYPO3 CMS versions from 10.0.0 to 14.0.1.
What causes CVE-2026-0859?
CVE-2026-0859 is caused by an insecure deserialization vulnerability within TYPO3's mailer file spool functionality.
Can CVE-2026-0859 be exploited remotely?
CVE-2026-0859 requires local user access to the spool directory, making remote exploitation unlikely without additional access.