by Kastro
Paper/Archive/CVE-2026-53512

CVE-2026-53512

better-auth better-auth — Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins

EPSS 0.3%CVSS 9.1
critical.is priorityof 100
31
CVSS 9.1 (CNA, NVD agree)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 20.0.200 × 204.0No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
better-auth< 1.6.11–CNA

Scores by source

GitHub_M (CNA)9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6hrefgithub.com/better-auth/better-auth/pull/9576refgithub.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659crefgithub.com/better-auth/better-auth/releases/tag/v1.6.11