Authentication Bypass in better-auth (CVE-2026-53512)
Summary
Authentication bypass in better-auth (CVE-2026-53512). Confidential information can be exposed externally. Exploitable via oauthApplication. 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. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. The @better-auth/oauth-provider package is not affected. 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-2026-53512 has been found in better-auth.
Attackers can target a specific entry point like oauthApplication over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: upgrade better-auth to 1.6.11 or later.
If unsure, ask your IT team or search "better-auth CVE-2026-53512" on the vendor's site.
CVE-2026-53512 (better-auth) — CWE-287 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: oauthApplication / trustedClients / mcp / oidcProvider
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.
Authentication bypass (CWE-287) exists in better-auth. Attackers reach the vulnerable code path via oauthApplication without authentication.
Check the vendor advisory for the affected versions of better-auth. Attack surface: oauthApplication / trustedClients / mcp / oidcProvider.
Severity: Critical (CVSS 9.1/10). 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 request patterns matching this CVE's known IOCs. Run grep -r 'better-auth' . 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' . | 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を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade better-auth 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を含めること。
-
3Post-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 nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- patch github.com
- web github.com
- web github.com