In September 2022, a critical security flaw was discovered in GitLab, one of the world’s most popular DevOps platforms. Tracked as CVE-2022-3285, this bug allows attackers to bypass the healthcheck endpoint’s allow list—a gatekeeper mechanism meant to ensure only certain IP addresses can access monitoring resources. In simple terms: an unauthorized attacker can stop GitLab from working for everyone, with little effort and no credentials.

What is the Healthcheck Endpoint in GitLab?

GitLab uses special network paths called "endpoints." The /-/health_check endpoint is a key tool often probed by load balancers, Kubernetes liveness probes, and monitoring software to make sure your GitLab instance is running and healthy.

To avoid misuse, you can set an Allow List: only IPs (addresses) you trust can call this endpoint. This should protect your server from denial of service and info leak attacks.

What Went Wrong? (Understanding CVE-2022-3285)

CVE-2022-3285 is a bypass vulnerability in the allow list filter for health check endpoints. In certain GitLab versions, *anyone* can trick the endpoint into thinking they’re allowed—sometimes, simply by tweaking a request! That means an attacker can hit your health endpoint repeatedly, or craft requests that *deny* access to the service for everyone else.

Technical Breakdown and Exploit Details

GitLab checks the "allow list" by looking at your IP address and sometimes at HTTP headers like X-Forwarded-For. A logic bug allowed attackers to send a request in a way that GitLab misinterpreted as coming from an allowed address—even if it wasn’t.

For example

- If your reverse proxy or load balancer (like NGINX) set certain headers, and you sent a crafted value for X-Forwarded-For, the allow list check could be skipped.
- In some cases, the endpoint could be outright disabled for everyone, denying access to health probes.

Here's a code snippet (Python, using requests) that shows how an attacker might try to access the healthcheck endpoint, bypassing the allow list:

import requests

url = "https://your-gitlab.example.com/-/health_check";

# Attacker tries to pose as an allowed IP (e.g., 127...1)
headers = {
    'X-Forwarded-For': '127...1',
    # Add more headers here if your proxy uses different ones
}

response = requests.get(url, headers=headers)

if response.status_code == 200:
    print("[+] Healthcheck endpoint bypassed!")
else:
    print("[-] Access denied or not vulnerable.")

TIP: Replace 127...1 with whatever IP is allowed in your GitLab configuration. Some installations use ::1 or custom ranges.

Malicious twist: Attackers could spam this endpoint, making your health checks fail, causing auto-scaling systems or orchestrators to *stop* or *restart* your GitLab container repeatedly—creating service outage for everyone!

References and Official Fixes

- GitLab Security Release – September 2022
- NVD Overview for CVE-2022-3285
- GitLab Issue Tracker – Internal (may require access)

15.4.1 or later

Apply the patch now, even if you use a private deployment. Vulnerabilities like this are simple to exploit, and proof-of-concept scripts are already circulating.

Conclusion

CVE-2022-3285 is a reminder that even defensive mechanisms can have holes. If you run GitLab, check your version, review your deployments, and update as soon as possible. It takes just a few HTTP headers to turn a "protected" healthcheck into a serious attack surface. Stay protected!

*Want to dig deeper?* Follow the official GitLab security blog for ongoing updates and best practices.


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Timeline

Published on: 11/09/2022 23:15:00 UTC
Last modified on: 11/11/2022 01:06:00 UTC