CVE-2026-59800

# Unauthenticated RCE via `/api/tunnel/tailscale-install` **Affected:** `9router` (npm package) — current master (`v0.4.39`). ### Summary `POST /api/tunnel/tailscale-install` accepts a JSON body with a `sudoPassword` field and pipes it, followed by the body of `https://tailscale.com/install.sh`, into a child process spawned as `sudo -S sh`. The route is not present in the dashboard middleware matcher in `src/proxy.js`, so the request reaches the handler without invoking `dashboardGuard.proxy()`. In deployments where the Node process runs as root (Docker images derived from `node:*` without a `USER` directive, `npm i -g 9router` invoked as root, or `systemd` units without `User=`), the spawned `sh` runs as root and executes the attacker-supplied bytes. ### Details #### 1. Middleware matcher (`src/proxy.js:3-15`) ```js export const config = { matcher: [ "/", "/dashboard/:path*", "/api/shutdown", "/api/settings/:path*", "/api/keys", "/api/keys/:path*", "/api/providers/client", "/api/provider-nodes/validate", "/api/cli-tools/:path*", "/api/mcp/:path*", ], }; ``` Next.js invokes the middleware only for paths matching this list. Routes that are not listed — including the entire `/api/tunnel/*` family — do not invoke `dashboardGuard.proxy()`. No cookie, JWT, CLI token, or `Host`-header check is applied to them. #### 2. Route handler (`src/app/api/tunnel/tailscale-install/route.js:18-67`) ```js export async function POST(request) { const body = await request.json().catch(() => ({})); ... const sudoPassword = body.sudoPassword || getCachedPassword() || await loadEncryptedPassword() || ""; ... const result = await installTailscale(sudoPassword, shortId, (msg) => { send("progress", { message: msg }); }); ... } ``` `body.sudoPassword` comes from the request body and is passed to `installTailscale`, which dispatches to `installTailscaleLinux` on Linux. #### 3. Linux installation routine (`src/lib/tunnel