Review reviewCritical

CVE-2026-9558

the affected product

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.

CVSS: 9.9
EPSS: -
CISA KEV: Not listed
Published: 2026.05.29

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability-

Technical severityCVSS 9.9

Vulnerability overview

Affected product and versions

Product: the affected product
Affected versions: >= 1.3.0 < 4.4.20, >= 5.0.0 < 5.2.11, >= 6.0.0 < 6.0.9, >= 7.0.0 < 7.1.2
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that the affected product and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CWE: CWE-1336