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Vulnerability record · CVE-2026-53518 · published 15 July 2026

CVE-2026-53518: Better-auth\/oauth-provider race condition vulnerability

Better Auth · Better Auth\/Oauth Provider

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.

7.6 CVSS 4.0 High EPSS 0.41% · top 67.4% CWE-362 · Race conditionCWE-367 · TOCTOU race condition
7.6CVSS 4.0 base score
0.41%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
3References
21 Jul 2026Last modified by NVD

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:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3ec9 Patch
https://github.com/better-auth/better-auth/releases/tag/v1.6.11 Release Notes
https://github.com/better-auth/better-auth/security/advisories/GHSA-7w99-5wm4-3g79 MitigationVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.6CVE-2026-53513Better-auth\/sso improper input validation vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the @better-auth/sso plugin's POST /sso/register and POST…EPSS 0.25%9.1CVE-2026-53512Better-auth better auth improper authentication vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth toke…EPSS 0.27%8.3CVE-2026-53516Better-auth better auth improper authentication vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, Better Auth's OAuth callback auto-link gate in handleOAut…EPSS 0.29%8.1CVE-2026-53517Better-auth\/oauth-provider race condition vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. From 1.4.8-beta.7 until 1.6.11, the @better-auth/oauth-provider POST /oaut…EPSS 0.42%7.9CVE-2024-56734Better-auth better auth open redirect vulnerabilityBetter Auth is an authentication library for TypeScript. An open redirect vulnerability has been identified in the verify email endpoint of all versi…EPSS 0.40%7.7CVE-2026-53514Better-auth better auth improper authentication vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, and in 1.6.14 and later when invitation IDs can be obtain…EPSS 0.20%7.6CVE-2026-45337Better-auth better auth improper authorization vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the deviceAuthorization plugin treats any authent…EPSS 0.21%7.1CVE-2026-53515Better-auth\/sso improper privilege management vulnerabilityBetter Auth is an authentication and authorization library for TypeScript. From 1.2.10 until 1.6.11, the @better-auth/sso plugin's POST /sso/register…EPSS 0.43%

Source: NIST National Vulnerability Database (record CVE-2026-53518), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.