CVE-2026-9558
Mautic’s theme engine renders uploaded Twig templates without restrictions, allowing authenticated users to upload malicious templates. This flaw lets attackers run arbitrary code on the server, giving them full control over the hosting environment.
No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.
Who is affected
Mautic platform versions that include the theme engine and permit authenticated users to create or upload themes.
Real-world impact
An attacker who can upload a theme can execute arbitrary code, read or modify system files, and compromise the entire server.
Why this severity
The CVSS score of 9.9 reflects that the vulnerability is network‑accessible, requires only low privilege, needs no user interaction, and can compromise confidentiality, integrity, and availability.
What to do about it
No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.
No fix documented in sources
Timeline
- May 29, 2026 · May 29, 2026PublishedDisclosed and added to the National Vulnerability Database.
- Jul 21, 2026 · 14d agoAdvisory updatedThe NVD record was last revised.