Origin Validation Error Affecting better-auth package, versions <1.7.16>=1.8.0-beta.0 <1.8.0-beta.5
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-BETTERAUTH-22193072
- published4 Nov 2026
- disclosed4 Nov 2026
- creditUnknown
Introduced: 4 Nov 2026
NewCVE-2026-121802 (opens in a new tab)How to fix?
Upgrade better-auth to version 1.7.16, 1.8.0-beta.5 or higher.
Overview
better-auth is a The most comprehensive authentication library for TypeScript.
Affected versions of this package are vulnerable to Origin Validation Error via the expo() plugin's public authorization-proxy endpoint, which signs a caller-supplied state value with the application secret without verifying that the server had previously issued that value. Because the same HMAC-SHA256 secret is used for email verification links and the session cookie cache, an attacker can forge an email-change token or a session cookie cache value that Better Auth accepts as legitimate. This allows an unauthenticated attacker who knows a target user's email address to take over the account and change its email address, and - when the session cookie cache is enabled - an attacker who knows a user's ID to act as that user.
Note: The session cookie cache attack vector is only exploitable when the session cookie cache feature is explicitly enabled.