High severity · published Jul 15, 2026
CVE-2026-53518
Better Auth OAuth Provider: Race Condition in Authorization Code Exchange Enables Multi-Use Code Redemption
8.1
CVSS
0.4%
EPSS
No
On KEV
Description
Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint for the authorization_code grant redeems a single-use authorization code through a non-atomic find-then-delete sequence, allowing two concurrent requests to pass the read step and mint independent access tokens, refresh tokens, and ID tokens; legacy /oauth2/token and /mcp/token paths in oidc-provider and mcp plugins share the same primitive. This issue is fixed in version 1.6.11.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BE
better-auth · better-auth
>= 1.6.0, < 1.6.11 · source: vendor
BA
Better Auth · Better-auth
1.6.0 before 1.6.11 · source: NVD
BE
Better-auth/oauth-provider · Better-auth
1.6.0 before 1.6.11 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53518
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53518
Patch
https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3ec9
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-7w99-5wm4-3g79
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