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CVE-2026-44476

Authentication Bypass in doorkeeper-openid_connect (CVE-2026-44476)

Summary

Authentication bypass in doorkeeper-openid_connect (CVE-2026-44476). Risk of unauthorized operations or information disclosure. Exploitable via POST /oauth/registration. Mitigation: upgrade to 1.10.0 or later.

Original description

The description as published by the source.

Impact

The DynamicClientRegistrationController#register action hard-codes confidential: false when creating applications (dynamic_client_registration_controller.rb:18-25), yet the response includes a client_secret and advertises token_endpoint_auth_methods_supported: ["client_secret_basic", "client_secret_post"].

Because Doorkeeper's Application.by_uid_and_secret treats a blank/missing secret as valid for non-confidential (public) clients, an
attacker who knows only the client_id (which is public information) can authenticate as the dynamically-registered client at the token endpoint.

Note that Dynamic Client Registration is opt-in feature which is disabled by default so only projects that explicitly enabled it are affected.

Steps to Reproduce

  1. Enable dynamic client registration in the initializer
  2. POST /oauth/registration with client_name, redirect_uris, and scope
  3. Observe: response returns client_secret, but the created
    Doorkeeper::Application has confidential: false
  4. Call Doorkeeper::Application.by_uid_and_secret(client_id, nil) — it
    returns the application (credentials bypass)
  5. POST /oauth/token with grant_type=client_credentials and only
    client_id (no client_secret) — the token endpoint issues an access token
    without any secret verification

Patches

Patched in 1.10.0

Workarounds

Upgrade existing applications created with a Dynamic Client registration to have confidential: true

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-2026-44476 has been found in doorkeeper-openid_connect.
Attackers can target a specific entry point like POST /oauth/registration over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade doorkeeper-openid_connect to 1.10.0 or later.
If unsure, ask your IT team or search "doorkeeper-openid_connect CVE-2026-44476" on the vendor's site.

CVE-2026-44476 (doorkeeper-openid_connect) — CWE-287
Attack surface: POST /oauth/registration / POST /oauth/token / Application.by_uid_and_secret
Patched: 1.10.0 — apply immediately
Workaround: Upgrade existing applications created with a Dynamic Client registration to have confidential: true
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

Authentication bypass (CWE-287) exists in doorkeeper-openid_connect. Attackers reach the vulnerable code path via POST /oauth/registration.

📍 Affected scope

Check the vendor advisory for the affected versions of doorkeeper-openid_connect. Attack surface: POST /oauth/registration / POST /oauth/token / Application.by_uid_and_secret.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.10.0.

🛡️ Workaround

Workaround: Upgrade existing applications created with a Dynamic Client registration to have confidential: true

🔍 Detection

Search webserver/proxy logs for unusual POST /oauth/registration requests with malformed payloads or SQL meta-characters. Run grep -r 'doorkeeper-openid_connect' . 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 'doorkeeper-openid_connect' . | 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 doorkeeper-openid_connect 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
    Hunt for indicators of compromise detect 
    grep 'POST /oauth/registration' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /oauth/registration への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply temporary workaround mitigate 
    Upgrade existing applications created with a Dynamic Client registration to have `confidential: true`

    パッチが適用されるまでの応急処置として、Upgrade existing applications created with a Dynamic Client registration to have confidential: true を実施。回避策の副作用 (機能低下) を確認した上で。

  4. 4
    Apply patch patch 
    Upgrade doorkeeper-openid_connect to 1.10.0

    ステージング環境で 1.10.0 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と、Step 2 で見つけた異常検知の続報チェックを含めること。

  5. 5
    Post-deployment verification verify 
    Replay attack against POST /oauth/registration on staging to confirm patch closes the vector

    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 Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

rubygems doorkeeper-openid_connect
[{"type":"ECOSYSTEM","events":[{"introduced":"1.9.0"},{"fixed":"1.10.0"}]}]

References

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