CVE-2026-53515: Better-Auth Better-Auth/sso

High severity, CVSS 7.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Better Auth is an authentication and authorization library for TypeScript. From 1.2.10 until 1.6.11, the @better-auth/sso plugin's POST /sso/register endpoint lets any organization member attach a new SSO provider to that organization because registerSSOProvider checks only for a membership row and does not require an owner or admin role, allowing attacker-controlled OIDC or SAML providers to drive /sso/callback/{providerId} organization provisioning. This issue is fixed in version 1.6.11.

Affected products

• Better-Auth Better-Auth/sso: before 1.6.11 (fixed in 1.6.11)
• Better-Auth Better Auth: from 1.2.10, before 1.6.11 (fixed in 1.6.11)

Published 2026-07-15. Last modified 2026-07-21.