PYSEC-2026-3830
Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)
Quick fix
PYSEC-2026-3830 — document-merge-service: upgrade to the fixed version with the command below.
pip install --upgrade 'document-merge-service>=9.1.0'Details
### 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](https://github.com/adfinis/document-merge-service/releases/tag/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
Are you affected?
Enter the version of the package you're using.
Affected packages
0Fixed in: 9.1.0pip install --upgrade 'document-merge-service>=9.1.0'References
- https://github.com/adfinis/document-merge-service/security/advisories/GHSA-w47q-945m-q9pc[WEB]
- https://github.com/adfinis/document-merge-service[PACKAGE]
- https://github.com/adfinis/document-merge-service/releases/tag/v9.1.0[WEB]
- https://pypi.org/project/document-merge-service[PACKAGE]
- https://github.com/advisories/GHSA-w47q-945m-q9pc[ADVISORY]
- https://nvd.nist.gov/vuln/detail/CVE-2026-53964[ADVISORY]