Vulnerability in @better-auth/oauth-provider (CVE-2026-53518)
Summary
Vulnerability in @better-auth/oauth-provider (CVE-2026-53518). Confidential information can be exposed externally. Exploitable via POST /oauth2/token. Mitigation: upgrade to 1.6.11 or later.
Original description
The description as published by the source.
Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint for the authorization_code grant redeems a single-use authorization code through a non-atomic find-then-delete sequence, allowing two concurrent requests to pass the read step and mint independent access tokens, refresh tokens, and ID tokens; legacy /oauth2/token and /mcp/token paths in oidc-provider and mcp plugins share the same primitive. This issue is fixed in version 1.6.11.
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-2026-53518 has been found in @better-auth/oauth-provider.
Attackers can target a specific entry point like POST /oauth2/token over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.1/10.
What to do: upgrade @better-auth/oauth-provider to 1.6.11 or later.
If unsure, ask your IT team or search "@better-auth/oauth-provider CVE-2026-53518" on the vendor's site.
CVE-2026-53518 (@better-auth/oauth-provider) — CWE-294 / CVSS v3 8.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: POST /oauth2/token / mcp / code / authorization_code
Patched: 1.6.11 — apply immediately
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-294) exists in @better-auth/oauth-provider. Attackers reach the vulnerable code path via POST /oauth2/token without authentication.
Check the vendor advisory for the affected versions of @better-auth/oauth-provider. Attack surface: POST /oauth2/token / mcp / code / authorization_code.
Severity: High (CVSS 8.1/10). Confidential information can be exposed externally.
Update to 1.6.11.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /oauth2/token requests with malformed payloads or SQL meta-characters. Run grep -r '@better-auth/oauth-provider' . 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 '@better-auth/oauth-provider' . | 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
@better-auth/oauth-providerを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /oauth2/token' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /oauth2/token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。 -
3Apply patch patch
Upgrade @better-auth/oauth-provider to 1.6.11ステージング環境で 1.6.11 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。
-
4Post-deployment verification verify
Replay attack against POST /oauth2/token 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
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- web github.com
- web github.com