CVE-2025-48865 Fabio allows HTTP clients to manipulate custom headers it adds
Attackers can remove or manipulate trusted X-Forwarded headers in Fabio, potentially bypassing security controls in backend applications.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-48865?
CVE-2025-48865 is a critical vulnerability in fabiolb fabio, published on 30 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Fabio is an HTTP(S) and TCP router for deploying applications managed by consul. Prior to version 1.6.6, Fabio allows clients to remove X-Forwarded headers (except X-Forwarded-For) due to a vulnerability in how it processes hop-by-hop headers. Fabio adds HTTP headers like X-Forwarded-Host and X-Forwarded-Port when routing requests to backend applications. Since the receiving application should trust these headers, allowing HTTP clients to remove or modify them creates potential security vulnerabilities. Some of these custom headers can be removed and, in certain cases, manipulated. The attack relies on the behavior that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been patched in version 1.6.6.
Which versions are affected by CVE-2025-48865?
3 open source packages ship an affected version, including github.com/fabiolb/fabio. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/fabiolb/fabio Go | All versions | 1.6.6 |
github.com/fabiolb/fabio Go | All versions | 1.6.6 |
github.com/fabiolb/fabio Go | All versions | 1.6.6 |
Products include Fabiolb Fabio.
How do I fix CVE-2025-48865?
Upgrade github.com/fabiolb/fabio to 1.6.6 or later.
Is CVE-2025-48865 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-48865 exists.
Sources
Also known as GHSA-q7p4-7xjv-j3wf, GO-2025-3722.