chi: Client IP spoofing in ClientIPFromXFF via X-Forwarded-For

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-114437: 0.13% estimated exploitation activity in the next 30 days; percentile 2.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary ClientIPFromXFF skips any X-Forwarded-For entry in a configured trusted CIDR but never verifies that the direct TCP peer in http.Request.RemoteAddr belongs to that CIDR. A client that can reach the Go server directly can therefore append a trusted-looking proxy address and choose the client IP returned by middleware.GetClientIP. The attack is remote and requires one unauthenticated HTTP request with no user interaction (AV:N/AC:L/PR:N/UI:N). It changes security decisions and exposes one protected handler within the same application (S:U/C:L/I:L); no availability loss was observed (A:N). Preconditions: The application uses ClientIPFromXFF and makes the origin server reachable by an anonymous client outside the configured trusted-proxy CIDRs. No victim interaction is required. 1. Send GET /admin directly to the origin with no X-Forwarded-For header. 2. Observe a 403 Forbidden response and an empty derived client IP. 3. Repeat the request with X-Forwarded-For: 10.0.0.7,…

Published by the source

23 Oct 2026, 20:56 UTC

Last modified by the source

23 Oct 2026, 21:15 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j6qf-3m9c-vwj3

2. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j6qf-3m9c-vwj3

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-j6qf-3m9c-vwj3

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-114437

Advisory: chi: Client IP spoofing in ClientIPFromXFF via X-Forwarded-For
IDs: CVE-2026-114437, GHSA-j6qf-3m9c-vwj3
Record: https://patchnext.com/advisories/cve-2026-114437 (revision 3, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/go-chi/chi/v5 5.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/go-chi/chi/v5: affected <= 5.3.2; fixed in 5.4.0

## Suggested inspection (read-only)
- Go github.com/go-chi/chi/v5: 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/go-chi/chi/v5.
- 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-j6qf-3m9c-vwj3 (OSV record GHSA-j6qf-3m9c-vwj3 lists affected ranges: Go github.com/go-chi/chi/v5 >=0 <5.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-j6qf-3m9c-vwj3 (GitHub-reviewed advisory GHSA-j6qf-3m9c-vwj3 lists affected ranges: Go github.com/go-chi/chi/v5 >=0 <=5.3.2)

Commands are suggestions: review each one before running it.