Auth bypass in Better-Auth
CVE-2026-53512
Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. The @better-auth/oauth-provider package is not affected. This issue is fixed in version 1.6.11.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (18.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 18.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Better-Auth — versions < 1.6.11
- Better-Auth Better Auth
Weakness classification (CWE)
References
- github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h (Mitigation, Vendor Advisory)
- github.com/better-auth/better-auth/pull/9576 (Patch, Issue Tracking)
- github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde356… (Patch)
- github.com/better-auth/better-auth/releases/tag/v1.6.11 (Release Notes)
Frequently asked questions
- What is CVE-2026-53512?
- CVE-2026-53512 is a critical-severity vulnerability in Better-Auth, classified under Improper Authentication. CVSS score: 9.1/10. Published 2026-07-15.
- How severe is CVE-2026-53512?
- Critical severity. CVSS v3 base score is 9.1 out of 10.