Authorization Flaw in Better Auth (CVE-2026-41427)
Summary
Vulnerability in Better Auth (CVE-2026-41427). Data can be tampered with by attackers. Mitigation: upgrade to 1.6.5 or later.
Original description
The description as published by the source.
Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.5, the clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted — any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata. This vulnerability is fixed in 1.6.5.
Source: NIST National Vulnerability Database NVD
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-2026-41427 has been found in Better Auth.
Data can be tampered with by attackers. CVSS score: 6.5/10.
What to do: upgrade Better Auth to 1.6.5 or later.
If unsure, ask your IT team or search "Better Auth CVE-2026-41427" on the vendor's site.
CVE-2026-41427 (Better Auth) — CWE-863 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Patched: 1.6.5 — 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.
Incorrect authorization (CWE-863) exists in Better Auth.
Check the vendor advisory for the affected versions of Better Auth.
Severity: Medium (CVSS 6.5/10). Data can be tampered with by attackers.
Update to 1.6.5.
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. Audit SBOM/dependencies 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
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Better Auth を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade Better Auth to 1.6.5ステージング環境で 1.6.5 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。
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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。