{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "better-auth"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.4.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-288"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-03T03:29:59Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "### Summary\n\nUnder 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.\n\n---\n\n### Description\n\nWhen 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.\n\nHowever, 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.\n\nThis results in a situation where session validity can be established before all authentication constraints are satisfied.\n\n---\n\n### Impact\n\nAn attacker (or user) with valid primary credentials may gain access to protected application routes without completing the required second authentication factor.\n\nAny application using `better-auth` with both two-factor authentication and session cookie caching enabled may be affected.\n\n---\n\n### Mitigation\n\n* Upgrade to a version of `better-auth` that includes the fix for this issue.\n* Ensure that session caching does not treat sessions as fully authenticated until all required authentication steps, including 2FA, are completed.\n* As a temporary workaround, disable `session.cookieCache` when using two-factor authentication.",
  "id": "GHSA-xg6x-h9c9-2m83",
  "modified": "2026-04-03T03:29:59Z",
  "published": "2026-04-03T03:29:59Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/better-auth/better-auth/security/advisories/GHSA-xg6x-h9c9-2m83"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/better-auth/better-auth"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Better Auth Has Two-Factor Authentication Bypass via Premature Session Caching (session.cookieCache)"
}