CVE-2026-9558
Mautic has Server-Side Template Injection (SSTI) in Theme Templates
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
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.
- Record
CVE-2026-9558- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-1336
- Updated
- 2026-11-02
EUVDEUVD-2026-33276
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.
- Record
EUVD-2026-33276- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-9fx4-7cmj-47vg
Mautic has Server-Side Template Injection (SSTI) in Theme Templates
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
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.
- Record
GHSA-9fx4-7cmj-47vg- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-1336
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-9558- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-1336
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2026-9558- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-1336
- Updated
- 2026-11-02
OSVGHSA-9fx4-7cmj-47vg
Mautic has Server-Side Template Injection (SSTI) in Theme Templates
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
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.
- Record
GHSA-9fx4-7cmj-47vg- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-1336
- Updated
- 2026-11-02
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mautic/corePackagist |
1.3.0 up to 4.4.13 | 4.4.13 |
mautic/corePackagist |
5.0.0 up to 5.2.11 | 5.2.11 |
mautic/corePackagist |
6.0.0 up to 6.0.9 | 6.0.9 |
mautic/corePackagist |
7.0.0 up to 7.1.2 | 7.1.2 |
mautic/corePackagist |
1.3.0 and later, plus listed versions 1.3.11.4.01.4.12.0.02.0.1 Show 45 moreShow less2.1.02.1.12.10.02.10.0-beta2.10.12.11.02.11.0-beta2.12.02.12.0-beta2.12.12.12.1-beta2.12.22.12.2-beta2.13.02.13.0-beta2.13.12.14.02.14.0-beta2.14.12.14.1-beta2.14.22.14.2-beta2.15.02.15.0-beta2.15.12.15.1-beta2.15.22.15.2-beta2.15.32.15.3-beta2.16.02.16.0-beta2.16.12.16.1-beta2.16.22.16.2-beta2.16.32.16.3-beta2.16.42.16.52.2.02.2.12.3.02.4.02.5.0 |
None known |
mautic/corePackagist |
5.0.0 up to 5.2.11, plus listed versions 5.0.15.0.25.0.35.0.45.1.0 Show 12 moreShow less5.1.15.2.05.2.15.2.105.2.25.2.35.2.45.2.55.2.65.2.75.2.85.2.9 |
5.2.11 |
mautic/corePackagist |
6.0.0 up to 6.0.9, plus listed versions 6.0.16.0.26.0.36.0.46.0.56.0.66.0.76.0.8 |
6.0.9 |
mautic/corePackagist |
7.0.0 up to 7.1.2, plus listed versions 7.0.17.0.27.1.07.1.0-rc7.1.1 |
7.1.2 |
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | Cimihan123/CVE-2026-9558-lab-poc-bundle | 2026-10-03 |
| PoC in GitHub | covepseng/cve-2026-9558-poc | 2026-07-10 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-9558 is a critical vulnerability (CVSS 9.9) in mautic/core, published May 29, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.57%, the 47th percentile. Fixed in mautic/core 4.4.13.
References
Left out here: 129 versions. The JSON record has them.