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

critical Affects mautic/core. Feed 2026.10.29.1, updated 2026-10-28; published 2026-07-02; advisory modified 2026-09-10.

Mautic has Server-Side Template Injection (SSTI) in Theme Templates

Package: mautic/core Composer
Affected versions: >=1.3.0 or >=5.0.0 and <5.2.11 or >=6.0.0 and <6.0.9 or >=7.0.0 and <7.1.2
Fixed in: no fix recorded
Severity: critical CVSS 9.9
Exploitation: not on CISA KEV · EPSS 1% (47.1th percentile)
Published: 2026-07-02
Source: osv.dev

References

CWE-1336

NVD record mautic/core advisories

Am I affected?

Find out in one command. phpwarden checks your composer.lock against this advisory and 20,000+ others, ranked by real-world exploitation (CISA KEV + EPSS). Free, offline, open data.

# one-time install
pip install phpwarden

# then
phpwarden deps composer.lock

Or keep it checked automatically: GitHub Action · pre-commit hook · GitLab CI · Laravel artisan command

Install docs How findings are ranked

Related advisories

CVE-2022-25772 critical Cross-site Scripting vulnerability in Mautic's tracking pixel functionality same package: mautic/core
CVE-2021-27909 medium XSS vulnerability on password reset page same package: mautic/core
CVE-2020-35125 critical Mautic is vulnerable to XSS vulnerability same package: mautic/core
CVE-2020-35124 critical XSS vulnerability leveraged through referrers could allow un-authorized admin access in Ma same package: mautic/core
CVE-2024-47051 critical Mautic allows Remote Code Execution and File Deletion in Asset Uploads same package: mautic/core
CVE-2020-35128 critical Mautic stored Cross-site Scripting (XSS) same package: mautic/core