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Advisory record · GHSA-q7p4-7xjv-j3wf

Fabio allows HTTP clients to manipulate custom headers it adds

CVSS 9.1 CriticalCriticalEPSS 0.0047 · 40th percentile

Critical, because:

  • CVSS score 9.1: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 29 May 2025, 16:50 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
github.com/fabiolb/fabioGo<1.6.61.6.6
Identifiers
GHSA-q7p4-7xjv-j3wf · CVE-2025-48865 · GO-2025-3722
Weakness (CWE)
CWE-345 · CWE-348
Tags
Published
29 May 2025
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Fabio versions before 1.6.6 are vulnerable. A client can list headers such as X-Forwarded-Host, X-Forwarded-Port, X-Forwarded-Proto, X-Real-Ip and Forwarded in the Connection header, which causes Fabio to strip them before the request reaches the backend. A backend that trusts these headers for access control could then be bypassed. Upgrade to Fabio 1.6.6 or later.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.1 Critical 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0047, the 40th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:14 UTC First seen by agentprime
  2. 31 Oct 2026, 14:14 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.