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Medium, CVSS 5.8amended

Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header

CVE-2026-62987GHSA-fq95-v8xc-jm3v

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/fabiolb/fabio 1.7.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
EPSS
  • CVE-2026-62987: 0.20% estimated exploitation activity in the next 30 days; percentile 10.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Affected: github.com/fabiolb/fabio = 1.6.6 through 1.7.1 and master HEAD (c75f8a6). Summary The v1.6.6 fix for CVE-2025-48865 sweeps the client Connection header against a hardcoded allowlist protectHeaders (proxy/httpheaders.go:28-36) containing only the 7 X-Forwarded family headers. Fabio also injects three operator-configured server-side trust headers that are NOT in that allowlist, so the original hop-by-hop stripping attack still works against them. Details The three unprotected trust headers and where fabio sets them: - ClientIPHeader (proxy.header.clientip) - httpheaders.go:73 r.Header.Set(cfg.ClientIPHeader, remoteIP) - TLSHeader (proxy.header.tls) - httpheaders.go:153 r.Header.Set(cfg.TLSHeader, cfg.TLSHeaderValue) (TLS connections) - RequestID (proxy.header.requestid) - httpproxy.go:90 r.Header.Set(p.Config.RequestID, id()) Order of operations in HTTPProxy.ServeHTTP: (1) line 90 sets RequestID; (2) line 175 calls addHeaders, which sweeps the Connection header (keeping the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-fq95-v8xc-jm3v

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6566

  3. Revision 1 · created ·

    Published from osv record GHSA-fq95-v8xc-jm3v

Agent brief

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# Patch Next advisory brief: CVE-2026-62987

Advisory: Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header
IDs: CVE-2026-62987, GHSA-fq95-v8xc-jm3v
Record: https://patchnext.com/advisories/cve-2026-62987 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/fabiolb/fabio 1.7.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/fabiolb/fabio: affected >= 1.6.6, <= 1.7.1; fixed in 1.7.2

## Suggested inspection (read-only)
- Go github.com/fabiolb/fabio: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/fabiolb/fabio.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-fq95-v8xc-jm3v (OSV record GHSA-fq95-v8xc-jm3v lists affected ranges: Go github.com/fabiolb/fabio >=1.6.6 <1.7.2 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6566 (OSV record GO-2026-6566 lists affected ranges: Go github.com/fabiolb/fabio >=1.6.6 <1.7.2 (fixed))
- Verified: https://github.com/advisories/GHSA-fq95-v8xc-jm3v (GitHub-reviewed advisory GHSA-fq95-v8xc-jm3v lists affected ranges: Go github.com/fabiolb/fabio >=1.6.6 <=1.7.1)

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