{"id":"CVE-2026-53518","aliases":["GHSA-7w99-5wm4-3g79"],"url":"https://o3.security/vulnerability/CVE-2026-53518","summary":"Better Auth OAuth Provider: Race Condition in Authorization Code Exchange Enables Multi-Use Code Redemption","details":"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.","published":"2026-07-15T17:17:06.410Z","modified":"2026-08-12T03:51:34.526954549Z","cvss":null,"epss":{"score":0.00229,"percentile":0.14007,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"@better-auth/oauth-provider","fixedVersion":"1.6.11"},{"ecosystem":"npm","name":"better-auth","fixedVersion":"1.6.11"}],"fix":{"url":"https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3ec9","label":"better-auth/better-auth@b4bc65a"},"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-2026-53518.json"},{"type":"ADVISORY","url":"https://github.com/better-auth/better-auth/security/advisories/GHSA-7w99-5wm4-3g79"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53518"},{"type":"FIX","url":"https://github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3ec9"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:34.526954549Z"}}