Critical severity · published Jul 15, 2026
CVE-2026-53512
Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins
9.1
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BE
better-auth · better-auth
< 1.6.11 · source: vendor
BA
Better Auth · Better-auth
before 1.6.11 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53512
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53512
Patch
https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c
Issue Tracking
https://github.com/better-auth/better-auth/pull/9576
Release Notes
https://github.com/better-auth/better-auth/releases/tag/v1.6.11
Mitigation
https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h
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