Vulnerability · Published Jul 15, 2026 · Assigned by GitHub_M

CVE-2026-53512Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins

Critical 9.1

In plain English

A critical-severity improper authentication 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 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)9.1Critical

Exploit odds (30 days)0.3%top 80.0% 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. 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	better-auth	1.6.11	GHSA-pw9m-5jxm-xr6h

Affected products (as reported)

Vendor	Product	Versions
better-auth	better-auth	< 1.6.11

Weakness: CWE-287, CWE-306, CWE-345, CWE-863 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h x_refsource_CONFIRM
https://github.com/better-auth/better-auth/pull/9576 x_refsource_MISC
https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c x_refsource_MISC
https://github.com/better-auth/better-auth/releases/tag/v1.6.11 x_refsource_MISC