Action Pack: Possible IP spoofing in Action Dispatch RemoteIp

Exploitation

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

CVSS

7.4 · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact Since Rails 8.1.0, `ActionDispatch::RemoteIp` derives `request.remote_ip` from `Rack::Request#forwarded_for`, which under Rack 3 reads the RFC 7239 `Forwarded` header in preference to `X-Forwarded-For`. When a reverse proxy appends the client address to `X-Forwarded-For` but passes a client-supplied `Forwarded` header through unchanged, `request.remote_ip` returns an address chosen by the client, and the IP spoofing check does not raise, because it compares only `Client-Ip` with the forwarded addresses. An unauthenticated attacker could therefore spoof `request.remote_ip`, possibly bypassing IP-based access controls and rate limits keyed on the client address (including the default `by:` of `rate_limit`), and falsifying the client address in logs.

Details The 8.1.0 change (2d084af8) switched `ActionDispatch::RemoteIp` from reading `X-Forwarded-For` directly to Rack's `forwarded_for`, in…

Published by the source

10 Nov 2026, 21:20 UTC

Last modified by the source

10 Nov 2026, 21:30 UTC

Source last checked

11 Nov 2026, 07:35 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-2gff-2mmg-m73p

2. Revision 1 · created · 10 Nov 2026

   Published from ghsa record GHSA-2gff-2mmg-m73p

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# Patch Next advisory brief: CVE-2026-126083

Advisory: Action Pack: Possible IP spoofing in Action Dispatch RemoteIp
IDs: CVE-2026-126083, GHSA-2gff-2mmg-m73p
Record: https://patchnext.com/advisories/cve-2026-126083 (revision 2, source checked 11 Nov 2026, 07:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: actionpack 8.1.4.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems actionpack: affected >= 8.1.0.beta1, < 8.1.4.1; fixed in 8.1.4.1

## Suggested inspection (read-only)
- RubyGems actionpack: 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 actionpack.
- 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-2gff-2mmg-m73p (GitHub-reviewed advisory GHSA-2gff-2mmg-m73p lists affected ranges: RubyGems actionpack >=8.1.0.beta1 <8.1.4.1)
- Verified: https://osv.dev/vulnerability/GHSA-2gff-2mmg-m73p (OSV record GHSA-2gff-2mmg-m73p lists affected ranges: RubyGems actionpack >=8.1.0.beta1 <8.1.4.1 (fixed))

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