Better Auth is an authentication and authorization library for TypeScript. In versions prior to 1.3.26, unauthenticated attackers can create or modify API keys for any user by passing that users id in the request body to the api/auth/api-key/create route. session?.user ?? (authRequired ? null : { id: ctx.body.userId }). When no session exists but userId is present in the request body, authRequired becomes false and the user object is set to the attacker-controlled ID. Server-only field validation only executes when authRequired is true (lines 280-295), allowing attackers to set privileged fields. No additional authentication occurs before the database operation, so the malicious payload is accepted. The same pattern exists in the update endpoint. This is a critical authentication bypass enabling full an unauthenticated attacker can generate an API key for any user and immediately gain complete authenticated access. This allows the attacker to perform any action as the victim user using the api key, potentially compromise the user data and the application depending on the victims privileges. Version 1.3.26 contains a patch for the issue.
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are not applied consistently - or not at all - users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.