Vulnerability in github.com/coder/coder/v2 (CVE-2026-55430)
Summary
Vulnerability in github.com/coder/coder/v2 (CVE-2026-55430). Confidential information can be exposed externally. Exploitable via Host. Mitigation: upgrade to 2.29.17 or later.
Original description
The description as published by the source.
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the workspace app proxy resolves the target app from httpapi.RequestHost() which prefers the X-Forwarded-Host header over the real Host header. No middleware strips X-Forwarded-Host before routing and the header is not browser-forbidden so client-side JavaScript can set it on fetch() calls. Practical exploitation requires subdomain app routing (wildcard hostname) enabled, a victim who visits the attacker's shared app and a deployment whose upstream proxy does not strip X-Forwarded-Host. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 trusts X-Forwarded-Host only from configured trusted proxies and otherwise resolves the routing host from the verified request host. As a workaround, place an upstream reverse proxy that strips or overwrites X-Forwarded-Host on untrusted requests.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-55430 has been found in github.com/coder/coder/v2.
Attackers can target a specific entry point like Host over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 5.8/10.
What to do: upgrade github.com/coder/coder/v2 to 2.29.17 or later.
If unsure, ask your IT team or search "github.com/coder/coder/v2 CVE-2026-55430" on the vendor's site.
CVE-2026-55430 (github.com/coder/coder/v2) — CWE-345 / CVSS v3 5.8
Attack vector: remote (network-reachable)
Attack surface: Host
Patched: 2.29.17 — apply immediately
Workaround: Place an upstream reverse proxy that strips or overwrites X-Forwarded-Host on untrusted requests.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-345) exists in github.com/coder/coder/v2. Attackers reach the vulnerable code path via Host.
Check the vendor advisory for the affected versions of github.com/coder/coder/v2. Attack surface: Host.
Severity: Medium (CVSS 5.8/10). Confidential information can be exposed externally.
Update to 2.29.17.
Workaround: Place an upstream reverse proxy that strips or overwrites X-Forwarded-Host on untrusted requests.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/coder/coder/v2' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'github.com/coder/coder/v2' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/coder/coder/v2を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Place an upstream reverse proxy that strips or overwrites `X-Forwarded-Host` on untrusted requests.パッチが適用されるまでの応急処置として、Place an upstream reverse proxy that strips or overwrites
X-Forwarded-Hoston untrusted requests. を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade github.com/coder/coder/v2 to 2.29.17ステージング環境で 2.29.17 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com