CVE-2026-9558
Critical
Description
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.
SeverityCritical
CVSS9.9
Exploit probability—
ProductMautic/core
PublishedMay 29, 2026
First seenMay 29, 2026
Weakness typeCWE-1336CWE-1336
How to fix
Update
- mautic/core5.2.11, 6.0.9, 7.1.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mautic/corePackagist | 1.3.0 ≤ v, 5.0.0 ≤ v < 5.2.11, 6.0.0 ≤ v < 6.0.9, 7.0.0 ≤ v < 7.1.2 | 5.2.11, 6.0.9, 7.1.2 |
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