Vulnerability in Better-Auth
CVE-2026-53518
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.
Vulnerability class: Race Condition
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (34.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Better-Auth — versions >= 1.6.0, < 1.6.11
- Better-Auth Better Auth
- Better-Auth Better-Auth\/oauth-Provider
Weakness classification (CWE)
References
- github.com/better-auth/better-auth/security/advisories/GHSA-7w99-5wm4-3g79 (Mitigation, Vendor Advisory)
- github.com/better-auth/better-auth/commit/b4bc65a007784b2eb0efb459e5fa6fd8055d3… (Patch)
- github.com/better-auth/better-auth/releases/tag/v1.6.11 (Release Notes)
Frequently asked questions
- What is CVE-2026-53518?
- CVE-2026-53518 is a high-severity vulnerability in Better-Auth, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 8.1/10. Published 2026-07-15.
- How severe is CVE-2026-53518?
- High severity. CVSS v3 base score is 8.1 out of 10.