Critical 9.1Published Jul 15, 2026

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

Updated under an hour ago (Oct 27, 2026, 7:50 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 9.1 CRITICAL (v4.0, CNA)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
Weakness (CWE): CWE-287, CWE-306, CWE-345, CWE-863
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Jul 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

better-auth better-auth better_auth:better_auth (from the name)	before 1.6.11	CNA record
better-auth better_auth better-auth:better_auth	before 1.6.11	NVD

References

References

https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h	x-refsource-confirm, mitigation, vendor-advisory
https://github.com/better-auth/better-auth/pull/9576	x-refsource-misc, issue-tracking, patch
https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c	x-refsource-misc, patch
https://github.com/better-auth/better-auth/releases/tag/v1.6.11	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.