CVE-2026-9558
A Server-Side Template Injection (SSTI) vulnerability exists in Mautic's theme engine. The platform renders uploaded Twig templates without a sandbox or strict function restrictions. Authenticated users with permissions to create or upload themes can abuse this to execute arbitrary code on the hosting server (Remote Code Execution) or access restricted system files and configuration settings.
- Affected products
- Mautic
- Fix
- Available
- CVSS 3.1
- 9.9 CRITICAL
- EPSS
- 0.6% (45th percentile)
- Weakness
- CWE-1336
- NVD status
- Deferred
- Published
- 2026-05-29
- Attack patterns
- CAPEC-242
Workaround
There are no official workarounds. To mitigate this vulnerability without upgrading, restrict theme upload and creation permissions (core:themes:create) to only highly trusted administrators.
CVE-2026-9558 at NVD
2 known exploits for CVE-2026-9558
Proof-of-concept code and exploit modules indexed by Sploitus