Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)
Impact
A remote code execution (RCE) via server-side template injection (SSTI) allows for user supplied code to be executed in the server's context where it is executed as the document-merge-server user with the UID 901 thus giving an attacker considerable control over the container. The vulnerability is limited to XLSX templates, were the xltpl library uses a npn-sandboxed Jinja environment for the processing of the template.
Patches
It has been patched in v9.1.0
Workarounds
Disable the upload/usage of XLSX templates.
References
Are there any links users can visit to find out more?
https://book.hacktricks.xyz/pentesting-web/ssti-server-side-template-injection/jinja2-ssti
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | document-merge-service | < 9.1.0 | 9.1.0 |
References
- https://github.com/adfinis/document-merge-service/security/advisories/GHSA-w47q-945m-q9pc
- https://github.com/adfinis/document-merge-service
- https://github.com/adfinis/document-merge-service/releases/tag/v9.1.0
- https://pypi.org/project/document-merge-service
- https://github.com/advisories/GHSA-w47q-945m-q9pc
- https://nvd.nist.gov/vuln/detail/CVE-2026-53964
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H- Weakness (CWE)
CWE-1336- Platform
- Python (PyPI)
- Package
document-merge-service- Disclosed
- 19.08.2026
- Updated
- 11.10.2026 15:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-3830 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-w47q-945m-q9pc - CC BY 4.0
Vulnerability history: document-merge-service
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 06.2024 08.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
Disclosures per year
- 2024: 1
- 2025: 0
- 2026: 1
-
Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes) this entry
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