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CVE-2026-67327 high CVSS 8.3

Authentication Bypass in better-auth (CVE-2026-67327)

Summary

Authentication bypass in better-auth (CVE-2026-67327). Confidential information can be exposed externally. Mitigation: upgrade to 1.7.0-beta.10 or later.

Original description

The description as published by the source.

Am I affected

You are affected if all of the following hold:

  • You run a better-auth version below 1.6.22, or a 1.7.0-beta below 1.7.0-beta.10.
  • You enable the magic-link plugin or the email-OTP plugin.
  • You also enable email and password sign-up with open registration.
  • An account can exist at an address before its owner first signs in with the passwordless flow.

Summary

An attacker can keep password access to a victim's account after the victim starts using it. The attack runs in three steps. First, with open registration, the attacker signs up using the victim's email and a password the attacker picks. The account stays unverified, so the attacker cannot use it yet. Later the real owner signs in with a magic link or an email OTP. That step marks the account verified, and the attacker's password now works on it.

Details

When an account already exists for an address, magic-link verification and email-OTP sign-in both sign in to that account. They mark it verified and issue a session. Before the fix, neither one removed a password set while the account was still unverified. Neither one revoked existing sessions. So a password set before anyone proved control of the mailbox kept working after the owner proved control.

This is a pre-account-hijacking weakness. It is the same class as the OAuth advisory GHSA-g38m-r43w-p2q7, applied to the passwordless email flows. Requiring email verification does not stop it. The verification step is the exact moment…

Source: NIST National Vulnerability Database 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-2026-67327 has been found in better-auth.
Confidential information can be exposed externally. CVSS score: 8.3/10.
What to do: upgrade better-auth to 1.7.0-beta.10 or later.
If unsure, ask your IT team or search "better-auth CVE-2026-67327" on the vendor's site.

CVE-2026-67327 (better-auth) — CWE-287 / CVSS v3 8.3
Attack vector: remote (network-reachable) / unauthenticated
Patched: 1.7.0-beta.10 — apply immediately
Workaround: If you cannot upgrade right away, you can lower the risk in two ways.
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 better-auth.

📍 Affected scope

Check the vendor advisory for the affected versions of better-auth.

🔥 Severity

Severity: High (CVSS 8.3/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 1.7.0-beta.10.

🛡️ Workaround

Workaround: If you cannot upgrade right away, you can lower the risk in two ways.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply temporary workaround mitigate 
    If you cannot upgrade right away, you can lower the risk in two ways.

    パッチが適用されるまでの応急処置として、If you cannot upgrade right away, you can lower the risk in two ways. 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 better-auth to 1.7.0-beta.10

    ステージング環境で 1.7.0-beta.10 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

npm better-auth
[{"type":"SEMVER","events":[{"introduced":"1.7.0-beta.0"},{"fixed":"1.7.0-beta.10"}]}]

References

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