Time-of-check Time-of-use (TOCTOU) Race Condition Affecting better-auth package, versions <1.6.11
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-17889820
- published8 Jul 2026
- disclosed7 Jul 2026
- creditDaniel Müller
Introduced: 7 Jul 2026
CVE-2026-53518 (opens in a new tab)How to fix?
Upgrade better-auth to version 1.6.11 or higher.
Overview
better-auth is a The most comprehensive authentication library for TypeScript.
Affected versions of this package are vulnerable to Time-of-check Time-of-use (TOCTOU) Race Condition through a race condition in the authorization_code grant handler. An attacker can obtain multiple valid access, refresh, and ID tokens for the same authorization code by sending concurrent requests to the token endpoint before the authorization code is deleted, thereby bypassing single-use enforcement.