Description

Detects JWT implementations vulnerable to algorithm switching attacks that allow the 'none' algorithm. If a JWT library accepts 'none' as the signing algorithm, attackers can forge valid tokens by stripping the signature, potentially bypassing authentication.

Detection Strategy

• Identifies imports of the 'jose' JWT library in the codebase

• Searches for JWT token verification code that could accept 'none' as an algorithm choice

• Reports vulnerability when JWT verification does not explicitly blacklist or reject the 'none' algorithm option

• Focuses on jose library usage patterns that may enable algorithm switching attacks

Vulnerable code example

import { JWT, JWK } from "jose";

// VULNERABLE: Accepts tokens with 'none' algorithm, allowing signature bypass
const token = JWT.verify("any-token", JWK.None);

✅ Secure code example

import { JWT } from "jose";

// Create a proper secret key
const secret = new TextEncoder().encode("your-secret-key"); 

// Secure: Explicitly specify allowed algorithms to prevent algorithm confusion attacks
const token = JWT.verify(receivedToken, secret, {
  algorithms: ["HS256"] // Only allow specific secure algorithms...