Vulnerability · Published Jul 15, 2026 · Assigned by GitHub_M

CVE-2026-53518Better Auth OAuth Provider: Race Condition in Authorization Code Exchange Enables Multi-Use Code Redemption

High 7.6

In plain English

A high-severity race condition in better-auth from better-auth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.6High

Exploit odds (30 days)0.4%top 64.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	@better-auth/oauth-provider	1.6.11	GHSA-7w99-5wm4-3g79
npm	better-auth	1.6.11	GHSA-7w99-5wm4-3g79

Affected products (as reported)

Vendor	Product	Versions
better-auth	better-auth	>= 1.6.0, < 1.6.11

Weakness: CWE-362, CWE-367 · Vector: 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

References

https://github.com/better-auth/better-auth/security/advisories/GHSA-7w99-5wm4-3g79 x_refsource_CONFIRM
https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3ec9 x_refsource_MISC
https://github.com/better-auth/better-auth/releases/tag/v1.6.11 x_refsource_MISC