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Vulnerabilities

Vulnerability · CVE-2026-9558

A Server-Side Template Injection (SSTI) vulnerability exists in Mautic's theme engine.

Published May 29, 2026 · catalog updated Jul 21, 2026 · A Server-Side Template Injection

Check if you run it

No confirmed exploitation is on record for CVE-2026-9558. EPSS is 0.79%. Act only if a listed version of A Server-Side Template Injection is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (A Server-Side Template Injection).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.79%
Remediation
Advisory link
Affected products
See sources for product scope

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.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-9558

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-9558. EPSS is 0.79%. Act only if a listed version of A Server-Side Template Injection is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine. EPSS 0.79%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. May 29, 2026 · NIST NVD

    Detected

    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.

  2. Jul 21, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2026-9558

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-9558

    30-day exploitation probability 0.8%

    first.org
  • NIST NVDVulnerability recordCVE-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 arbitra

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.