---
id: CVE-2026-9558
title: Mautic has Server-Side Template Injection (SSTI) in Theme Templates
summary: Mautic has Server-Side Template Injection (SSTI) in Theme Templates
severity: critical
cvss: 9.9
cwe:
  - CWE-1336
vendor: mautic
product: mautic/core
ecosystem: composer
affected:
  - 'mautic/core >= 1.3.0, < 4.4.13'
  - 'mautic/core >= 5.0.0, < 5.2.11'
  - 'mautic/core >= 6.0.0, < 6.0.9'
  - 'mautic/core >= 7.0.0, < 7.1.2'
patched:
  - mautic/core 5.2.11
  - mautic/core 6.0.9
  - mautic/core 7.1.2
published: '2026-07-02'
updated: '2026-07-02'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-9fx4-7cmj-47vg'
references:
  - url: 'https://github.com/mautic/mautic/security/advisories/GHSA-9fx4-7cmj-47vg'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-9558'
  - url: 'https://github.com/advisories/GHSA-9fx4-7cmj-47vg'
tags:
  - ghsa
  - composer
  - exploit-available
epss: 0.00571
epssPercentile: 0.45728
ingestedAt: '2026-07-02T20:42:45.859Z'
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/covepseng/cve-2026-9558-poc'
  checkedAt: '2026-09-21T15:31:32.320Z'
exploitAvailable: true
---

## Overview

### Summary
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.

### Impact
An authenticated user with theme upload and creation privileges can bypass boundaries to execute arbitrary system commands on the hosting server (Remote Code Execution) or access restricted system files and configuration settings.

### Patched Versions
This security issue has been addressed in the following releases:
* **7.1.2**
* **6.0.9**
* **5.2.11**

For users on Mautic 4.x, this fix is available in:
* **4.4.20** via [ELTS](https://mautic.org/extended-long-term-support-elts/)

Mautic strongly recommend upgrading to a patched version immediately.

### Workarounds
There are no official workarounds. To mitigate this vulnerability without upgrading, restrict theme upload and creation permissions (`core:themes:create`) to only highly trusted administrators.

## Affected packages

- `mautic/core >= 1.3.0, < 4.4.13`
- `mautic/core >= 5.0.0, < 5.2.11`
- `mautic/core >= 6.0.0, < 6.0.9`
- `mautic/core >= 7.0.0, < 7.1.2`

## Remediation

Upgrade to a patched release:

- `mautic/core 5.2.11`
- `mautic/core 6.0.9`
- `mautic/core 7.1.2`