Vulnerability in github.com/coder/coder/v2 (CVE-2026-55427)
Summary
Vulnerability in github.com/coder/coder/v2 (CVE-2026-55427). Successful exploitation can lead to full system takeover. Exploitable via HostnameSuffix. 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, coder config-ssh wrote server-supplied SSH settings (HostnameSuffix, SSHConfigOptions) into the user's ~/.ssh/config without sanitizing embedded newlines or restricting directives so a malicious or compromised Coder server could inject arbitrary SSH configuration. Practical exploitation requires control of the server-supplied values through a malicious or compromised deployment, a man-in-the-middle position or admin access to the HostnameSuffix and SSHConfigOptions settings. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 validates HostnameSuffix and SSHConfigOptions against a strict character set that rejects newlines and other control characters. As a workaround, inspect coder config-ssh --dry-run output before applying changes.
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-2026-55427 has been found in github.com/coder/coder/v2.
Attackers can target a specific entry point like HostnameSuffix over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.3/10.
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-2026-55427" on the vendor's site.
CVE-2026-55427 (github.com/coder/coder/v2) — CWE-74 / CVSS v3 8.3
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: HostnameSuffix / SSHConfigOptions / ProxyCommand
Patched: 2.29.17 — apply immediately
Workaround: Inspect coder config-ssh --dry-run output before applying changes.
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-74) exists in github.com/coder/coder/v2. Attackers reach the vulnerable code path via HostnameSuffix without authentication.
Check the vendor advisory for the affected versions of github.com/coder/coder/v2. Attack surface: HostnameSuffix / SSHConfigOptions / ProxyCommand.
Severity: High (CVSS 8.3/10). Successful exploitation can lead to full system takeover.
Update to 2.29.17.
Workaround: Inspect coder config-ssh --dry-run output before applying changes.
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
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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
Inspect `coder config-ssh --dry-run` output before applying changes.パッチが適用されるまでの応急処置として、Inspect
coder config-ssh --dry-runoutput before applying changes. 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