# CVE-2026-126083: Action Pack: Possible IP spoofing in Action Dispatch RemoteIp


- **Severity:** High 7.4 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** GHSA-2gff-2mmg-m73p, UBUNTU-CVE-2026-126083

## What is CVE-2026-126083?

CVE-2026-126083 is a high-severity vulnerability in rails, published on 10 Nov 2026. 

### Official description

Action Pack is a framework for handling and responding to web requests. From 8.1 until 8.1.4.1, 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. An application is affected if it meets all of these requirements: Runs Rails 8.1.0 through 8.1.4 with Rack 3. Under Rack 2.2, forwarded_for reads only X-Forwarded-For. Is served behind a proxy that does not remove or overwrite a client-supplied Forwarded header. Relies on request.remote_ip for access control, rate limiting, or auditing. The fix detects a spoofed Forwarded header only when the proxy also sets X-Forwarded-For. An application whose proxy passes a client-supplied Forwarded header through and sets no X-Forwarded-For remains exposed after upgrading, and should configure the proxy to remove or overwrite Forwarded, or apply the workaround below. This issue is fixed in version 8.1.4.1.

Weakness: CWE-348 (Use of Less Trusted Source)

## Which versions are affected by CVE-2026-126083?

1 open source package ship an affected version, including actionpack.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `actionpack` | RubyGems | From 8.1.0.beta1 | 8.1.4.1 |

## How do I fix CVE-2026-126083?

Upgrade actionpack to 8.1.4.1 or later.

## Is CVE-2026-126083 being exploited?

There is no known exploitation of CVE-2026-126083 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126083 and fix it if it is affected.

What it is: CVE-2026-126083 is a high-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126083 in the wild and no public exploit code.

Affected packages and fixed versions:
- actionpack (RubyGems): affected from 8.1.0.beta1; fixed in 8.1.4.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126083/ (Markdown: https://insights.sbomify.com/CVE-2026-126083/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126083
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126083
- OSV: https://osv.dev/vulnerability/CVE-2026-126083

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126083/
Summaries are generated and may contain mistakes; the official description above is the record.