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

Advisory record · `GHSA-j6qf-3m9c-vwj3`

- **Identifiers:** `GHSA-j6qf-3m9c-vwj3` · `CVE-2026-114437`
- **State:** Confirmed
- **Severity:** CVSS 6.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-345](https://cwe.mitre.org/data/definitions/345.html) · [CWE-348](https://cwe.mitre.org/data/definitions/348.html)
- **Tags:** [CWE-345](https://agentprime.io/advisories/tag/cwe-345.md) · [CWE-348](https://agentprime.io/advisories/tag/cwe-348.md)
- **Published:** 23 Oct 2026
- **Updated:** 23 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 23 Oct 2026, 20:56 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/go-chi/chi/v5` (Go): affected `<5.4.0`; fixed in `5.4.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The chi package github.com/go-chi/chi/v5 before 5.4.0 is vulnerable in its ClientIPFromXFF middleware, which does not verify that the direct TCP peer belongs to a configured trusted proxy CIDR before trusting X-Forwarded-For entries. An unauthenticated attacker who can reach the server directly can send a forged X-Forwarded-For header to make the client IP appear as an allowlisted address, which can bypass IP-based access controls. Upgrade to version 5.4.0 or later. The source gives no workaround.

Written 1 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`, from CNA (tenable)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0013, the 2nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:11 UTC: First seen by agentprime
- 31 Oct 2026, 14:11 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-j6qf-3m9c-vwj3)

## Sources

- [GitHub Advisory Database: GHSA-j6qf-3m9c-vwj3](https://github.com/advisories/GHSA-j6qf-3m9c-vwj3)
- [OSV: GHSA-j6qf-3m9c-vwj3](https://osv.dev/vulnerability/GHSA-j6qf-3m9c-vwj3)
- <https://github.com/go-chi/chi/security/advisories/GHSA-j6qf-3m9c-vwj3>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-114437>
- <https://github.com/go-chi/chi/pull/1214>
- <https://github.com/go-chi/chi/commit/7f9b7448f51d28804fac98c0a17bc2a7cec1079f>
- <https://github.com/go-chi/chi>
- <https://github.com/go-chi/chi/releases/tag/v5.4.0>
- <https://www.tenable.com/security/research/tra-2026-66>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-j6qf-3m9c-vwj3>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-j6qf-3m9c-vwj3/>. Everything for agents: <https://agentprime.io/llms.txt>.