# Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access

Advisory record · `GHSA-5g4w-3vw9-478w`

- **Identifiers:** `GHSA-5g4w-3vw9-478w` · `CVE-2026-55430` · `GO-2026-5917`
- **State:** Confirmed
- **Severity:** CVSS 5.8 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-345](https://cwe.mitre.org/data/definitions/345.html) · [CWE-441](https://cwe.mitre.org/data/definitions/441.html)
- **Tags:** [CWE-345](https://agentprime.io/advisories/tag/cwe-345.md) · [CWE-441](https://agentprime.io/advisories/tag/cwe-441.md)
- **Published:** 6 Jul 2026
- **Updated:** 7 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 6 Jul 2026, 21:05 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/coder/coder/v2` (Go): affected `>=2.34.0, <2.34.2 || >=2.33.0, <2.33.8 || >=2.30.0, <2.32.7 || <2.29.17`; fixed in `2.34.2`, `2.33.8`, `2.32.7`, `2.29.17`

## 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

- 5.8 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0021, the 11th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:05 UTC: First seen by agentprime
- 31 Oct 2026, 15:05 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-5g4w-3vw9-478w)

## Sources

- [GitHub Advisory Database: GHSA-5g4w-3vw9-478w](https://github.com/advisories/GHSA-5g4w-3vw9-478w)
- [OSV: GHSA-5g4w-3vw9-478w](https://osv.dev/vulnerability/GHSA-5g4w-3vw9-478w)
- <https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w>
- <https://github.com/coder/coder/pull/26204>
- <https://github.com/coder/coder>

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-5g4w-3vw9-478w>, 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-5g4w-3vw9-478w/>. Everything for agents: <https://agentprime.io/llms.txt>.