CVE-2026-67333: Better-Auth

High severity, CVSS 7.2. EPSS: 0.3% chance of exploitation in the next 30 days.

better-auth before 1.6.13 (and pre-release builds 1.7.0-beta.0 through 1.7.0-beta.3) fail to validate the scheme of redirect_uris registered via the deprecated oidc-provider plugin and the mcp plugin (which wraps the same provider). An attacker can register an OAuth client with a javascript: redirect_uri, which the authorization server later returns unchanged in the consent response. If the deployment's consent page navigates the browser to the returned redirectURI (e.g. assigning it to window.location.href), the attacker's JavaScript executes in the authorization-server origin, exposing the victim's session and enabling account takeover.

Affected products

• Better-Auth Better-Auth: before 1.6.13 (fixed in 1.6.13); from 1.7.0-beta.0, before 1.7.0-beta.4 (fixed in 1.7.0-beta.4)

Published 2026-08-01. Last modified 2026-09-08.