CVE-2026-110863 [HIGH] – Better Auth @better-auth/sso from 1.7.0-rc.2 before 1.7.3 contains an authentication bypas

Better Auth @better-auth/sso from 1.7.0-rc.2 before 1.7.3 contains an authentication bypass vulnerability that allows authenticated users to sign in as other users by registering a personal SSO provider. Attackers can copy a legitimate provider’s OIDC issuer or SAML entity ID and assert a victim’s subject or NameID, because account lookup ignores providerId, creating sessions for victim accounts.