CVE-2026-9558: Mautic has Server-Side Template Injection (SSTI) in Theme Templates

July 2, 2026

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.

References

github.com/advisories/GHSA-9fx4-7cmj-47vg
github.com/mautic/mautic/security/advisories/GHSA-9fx4-7cmj-47vg
nvd.nist.gov/vuln/detail/CVE-2026-9558

Code Behaviors & Features

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