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CVE-2026-67337 medium CVSS 6.5

Vulnerability in better-auth (CVE-2026-67337)

Summary

Vulnerability in better-auth (CVE-2026-67337). Confidential information can be exposed externally. Exploitable via session.cookieCache. Mitigation: upgrade to 1.4.9 or later.

Original description

The description as published by the source.

Summary

Under certain configurations, sessions may be considered valid before two-factor authentication (2FA) is fully completed. This can allow access to authenticated routes without verifying the second factor.

Description

When two-factor authentication is enabled, the authentication flow correctly identifies users who require additional verification and defers full authentication until the second factor is completed.

However, when session.cookieCache is enabled, the session generated during the initial sign-in step may be cached as valid prior to 2FA verification. Subsequent session lookups may then return this cached session without re-evaluating the 2FA requirement.

This results in a situation where session validity can be established before all authentication constraints are satisfied.

Impact

An attacker (or user) with valid primary credentials may gain access to protected application routes without completing the required second authentication factor.

Any application using better-auth with both two-factor authentication and session cookie caching enabled may be affected.

Mitigation

  • Upgrade to a version of better-auth that includes the fix for this issue.
  • Ensure that session caching does not treat sessions as fully authenticated until all required authentication steps, including 2FA, are completed.
  • As a temporary workaround, disable session.cookieCache when using two-factor authentication.

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-2026-67337 has been found in better-auth.
Attackers can target a specific entry point like session.cookieCache over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.5/10.
What to do: upgrade better-auth to 1.4.9 or later.
If unsure, ask your IT team or search "better-auth CVE-2026-67337" on the vendor's site.

CVE-2026-67337 (better-auth) — CWE-288 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: session.cookieCache
Patched: 1.4.9 — 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.

❓ What is the problem

A vulnerability (CWE-288) exists in better-auth. Attackers reach the vulnerable code path via session.cookieCache.

📍 Affected scope

Check the vendor advisory for the affected versions of better-auth. Attack surface: session.cookieCache.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 1.4.9.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 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 patch patch 
    Upgrade better-auth to 1.4.9

    ステージング環境で 1.4.9 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。

  3. 3
    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":"0"},{"fixed":"1.4.9"}]}]

References

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