{"id":"CVE-2026-53512","aliases":["GHSA-pw9m-5jxm-xr6h"],"url":"https://o3.security/vulnerability/CVE-2026-53512","summary":"Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider and mcp plugins","details":"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.","published":"2026-07-15T17:18:09.512Z","modified":"2026-08-12T03:51:46.867830779Z","cvss":null,"epss":{"score":0.00275,"percentile":0.19373,"asOf":"2026-08-25"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"better-auth","fixedVersion":"1.6.11"}],"fix":{"url":"https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c","label":"better-auth/better-auth@1f2ff42"},"references":[{"type":"WEB","url":"https://github.com/better-auth/better-auth/releases/tag/v1.6.11"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53512.json"},{"type":"ADVISORY","url":"https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53512"},{"type":"FIX","url":"https://github.com/better-auth/better-auth/commit/1f2ff4215c4affff0b140b0c0a712c0dde35659c"},{"type":"FIX","url":"https://github.com/better-auth/better-auth/pull/9576"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:46.867830779Z"}}