CVE-2026-73421
CriticalCVSS 9.1Summary
NextAuth.js from 5.0.0-beta.0 until 5.0.0-beta.32 has a vulnerability where applications that gate access by checking only for the existence of the auth object can fail open when Auth.js has a server configuration error. A non-OK session response is parsed into a truthy error object instead of null, so checks such as !!auth evaluate to true for unauthenticated requests.
Risk Assessment
After a misconfiguration, routes protected only by session existence silently grant access to every visitor, leading to unauthorized access to data and functions.
Recommendation
Upgrade NextAuth.js to version 5.0.0-beta.32, which contains the fix.
Original NVD description (English source)
NextAuth.js provides authentication for Next.js. From next-auth 5.0.0-beta.0 until 5.0.0-beta.32, applications that gate access by checking only for the existence of the auth object returned by the auth() wrapper can fail open when Auth.js has a server configuration error. In middleware, Route Handlers, React Server Components, and other auth() entry points, a non-OK session response is parsed into a truthy error object instead of null, so checks such as !!auth and if (req.auth) evaluate to true for unauthenticated requests. A provider missing both the issuer and authorization endpoint triggers InvalidEndpoints, and an unset AUTH_SECRET or another server configuration error can produce the same behavior. There is no impact while configuration is valid, but after a deployment becomes misconfigured, routes protected only by session existence silently grant access to every visitor. This issue is fixed in next-auth 5.0.0-beta.32.