Vulnerability Details CVE-2026-53518
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.005
EPSS Ranking 39.3%
CVSS Severity
CVSS v3 Score 8.1
References
Products affected by CVE-2026-53518
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.0
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.1
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.10
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.2
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.3
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.4
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.5
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.6
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.7
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.8
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cpe:2.3:a:better-auth:better-auth/oauth-provider:1.6.9