CVE-2026-45773: Turbo: Login callback CSRF/session fixation

Turborepo’s self-hosted login and SSO browser flows did not validate a CSRF state value on the localhost callback. While the CLI was waiting for authentication, a malicious web page could send a request to the local callback server with an attacker-controlled token. If accepted before the legitimate callback, the CLI could complete login with the wrong credentials.

This affects users authenticating the turbo CLI against self-hosted remote cache/auth endpoints. Vercel-hosted login flows using device authorization are not affected.