TYPO3 CMS Insecure Deserialization Vulnerability
CVE-2026-0859
Released: January 13, 2026
Last Updated: January 13, 2026
Vendor: TYPO3
Attack Tags: TYPO3 CMS, PHP, Insecure Deserialization, Local Privilege Escalation, Remote Code Execution
Severity: Medium
What is CVE-2026-0859?
CVE-2026-0859 is a medium-severity security vulnerability affecting TYPO3 CMS. The issue stems from insecure deserialization in TYPO3’s mailer file spool mechanism, which is used to queue and process outgoing emails.
Due to insufficient validation of serialized data, TYPO3 may process maliciously crafted spool files. If exploited, this can allow attackers with local write access to execute arbitrary PHP code on the web server, potentially leading to full application compromise.
Affected Versions
The vulnerability impacts the following TYPO3 CMS versions:
- 12.0.0 – 12.4.40
- 13.0.0 – 13.4.22
- 14.0.0 – 14.0.1
Organizations running these versions should consider themselves at risk until patched.
Observed Attack Activity
At the time of disclosure, there is no confirmed large-scale internet exploitation of CVE-2026-0859. However, this vulnerability is highly relevant in post-compromise scenarios, such as:
- Abuse by attackers who already gained limited system access
- Exploitation via vulnerable or misconfigured TYPO3 extensions
- Shared hosting environments with weak file permission controls
Once exploited, attackers can escalate privileges and gain persistent control over the TYPO3 environment.
Additional Resources
For more detailed technical information and official advisories, refer to the following sources:
- CVE.org – Official CVE Record
https://www.cve.org/CVERecord?id=CVE-2026-0859 - TYPO3 Security Advisories
https://typo3.org/security/advisory - OpenCVE – CVE Tracking & Updates
https://app.opencve.io/cve/CVE-2026-0859 - NVD – National Vulnerability Database
https://nvd.nist.gov/vuln/detail/CVE-2026-0859
How We Can Help
Security issues like CVE-2026-0859 highlight the importance of continuous monitoring and proactive patch management.
Our security teams help organizations by providing:
- Continuous vulnerability assessment and patch management
- TYPO3 CMS security hardening and configuration reviews
- 24×7 monitoring and incident response support
- Compliance-aligned security reporting
Connect with our security experts to reduce risk and keep your CMS environments secure.