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High, CVSS 7.7

chi Middleware Vulnerable to Potential IP Spoofing via X-Forwarded-For Header in Request.RemoteAddr Resolution

GHSA-9g5q-2w5x-hmxf

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

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

  • Go github.com/go-chi/chi/v2/middleware

    Affected
    <= 2.1.1
    Fixed in
    no fixed version recorded

  • Go github.com/go-chi/chi/v3/middleware

    Affected
    <= 3.3.5
    Fixed in
    no fixed version recorded

  • Go github.com/go-chi/chi/v5/middleware

    Affected
    < 5.3.0
    Fixed in
    5.3.0

  • Go github.com/go-chi/chi/v4/middleware

    Affected
    <= 4.1.3
    Fixed in
    no fixed version recorded

  • Go github.com/go-chi/chi/middleware

    Affected
    >= 0.9.0, <= 1.5.5
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
7.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Summary The vulnerability allows the Request.RemoteAddr to be spoofed when determining the request source IP via the X-Forwarded-For header. This could result in misidentification of the request source and potentially compromise access control and logging integrity. Details Currently, the RealIP() implementation splits the X-Forwarded-For header by , and uses the first IP. https://github.com/go-chi/chi/blob/v5.1.0/middleware/realip.go#L50-L54 However, relying on the first IP in the X-Forwarded-For header is insecure because it can be manipulated by attackers to falsify the source IP. Malicious Case: 1. A malicious client sends a request with a forged IP in the X-Forwarded-For header: X-Forwarded-For: <forged-ip 2. The proxy appends the actual client’s IP and forwards the request: X-Forwarded-For: <forged-ip,<client-ip 3. If the server always uses the first IP, it becomes vulnerable to IP spoofing. Ideally, the implementation should verify IPs starting from the end of the…

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

    Published from ghsa record GHSA-9g5q-2w5x-hmxf

Agent brief

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

# Patch Next advisory brief: GHSA-9g5q-2w5x-hmxf

Advisory: chi Middleware Vulnerable to Potential IP Spoofing via `X-Forwarded-For` Header in `Request.RemoteAddr` Resolution
IDs: GHSA-9g5q-2w5x-hmxf
Record: https://patchnext.com/advisories/ghsa-9g5q-2w5x-hmxf (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/go-chi/chi/v5/middleware 5.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/go-chi/chi/v2/middleware: affected <= 2.1.1
- Go github.com/go-chi/chi/v3/middleware: affected <= 3.3.5
- Go github.com/go-chi/chi/v5/middleware: affected < 5.3.0; fixed in 5.3.0
- Go github.com/go-chi/chi/v4/middleware: affected <= 4.1.3
- Go github.com/go-chi/chi/middleware: affected >= 0.9.0, <= 1.5.5

## Suggested inspection (read-only)
- Go github.com/go-chi/chi/v2/middleware: check the installed version with your package manager.
- Go github.com/go-chi/chi/v3/middleware: check the installed version with your package manager.
- Go github.com/go-chi/chi/v5/middleware: check the installed version with your package manager.
- Go github.com/go-chi/chi/v4/middleware: check the installed version with your package manager.
- Go github.com/go-chi/chi/middleware: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/go-chi/chi/v2/middleware, github.com/go-chi/chi/v3/middleware, github.com/go-chi/chi/v5/middleware, github.com/go-chi/chi/v4/middleware, github.com/go-chi/chi/middleware.
- 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://github.com/advisories/GHSA-9g5q-2w5x-hmxf (GitHub-reviewed advisory GHSA-9g5q-2w5x-hmxf lists affected ranges: Go github.com/go-chi/chi/middleware >=0.9.0 =0 =0 =0 =0 <5.3.0)

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