Track vulnerabilities like this one. Sign up free to get alerted when software you use is affected.

CVE-2025-48865: Fabio router lets clients change forwarding headers

CVE-2025-48865 · published 1 year ago

Summary

The Fabio routing software adds information about the original request in special headers that backend services rely on. Before version 1.6.6, a user could remove or alter some of these headers, which could let an attacker disguise the true source of a request. Upgrade Fabio to version 1.6.6 or newer to stop this behavior.

What to do

Update github.com fabiolb to version 1.6.6.
Update fabiolb fabio to version 1.6.6 or later.

Affected software

Ecosystem	Vendor	Product	Affected versions
go	github.com	fabiolb	<= 1.6.5 Fix: upgrade to 1.6.6
–	fabiolb	fabio	< 1.6.6 `cpe:2.3:a:fabiolb:fabio::::::go::*`

Original advisory text

Fabio allows HTTP clients to manipulate custom headers it adds

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.

References

https://github.com/advisories/GHSA-q7p4-7xjv-j3wf
https://github.com/fabiolb/fabio/releases/tag/v1.6.6 URL
https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/48xxx/CVE-2025-48865... Vendor Advisory
https://github.com/fabiolb/fabio/security/advisories/GHSA-q7p4-7xjv-j3wf Vendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2025-48865 Vendor Advisory
https://github.com/fabiolb/fabio/commit/fdaf1e966162e9dd3b347ffdd0647b39dc71a1a3 Patch

Fix within

Internet-facing 3 days

Internal 60 days

Not known to be exploited
Can be exploited automatically
Gives an attacker full control

Severity

9.1 Critical

Exploitation

<1% chance of attack within 30 days

Type

CWE-345Insufficient Verification of Data Authenticity

CWE-348Use of Less Trusted Source

Timeline

Published30 May 2025

Updated4 Nov 2026

First seen6 Mar 2026

Sources

GHSA-q7p4-7xjv-j3wf · GHSA

CVE-2025-48865 · NVD

CVE-2025-48865 · OSV

Track software like this

Free during beta