CVE-2026-56682: 9Router has a Login Brute-Force Lockout Bypass via Spoofable X-9r-Real-Ip Header

9router enforces a progressive login lockout (5 failed attempts → temporary 30s+ lock) keyed on the client IP. The client IP used for this limiter is taken from the X-9r-Real-Ip request header, which is intended to be set only by the bundled custom-server.js layer from the unspoofable TCP socket address. In deployment modes where requests reach Next.js directly, a remote attacker controls this header and can assign a unique value to every request. Because each distinct header value maps to a fresh limiter bucket, the lockout never triggers, enabling unlimited password guessing against the dashboard login endpoint. This was reproduced against a live instance: a fixed header value was locked out (429) after 5 attempts, while rotating the header produced unlimited 401 responses with no lockout.