Description

Detects when sensitive information may be exposed through insecure JWT token generation in C# applications. This vulnerability occurs when sensitive claims or data are included in JWT tokens without proper protection, potentially exposing confidential information to client-side code.

Detection Strategy

• Verifies that both System.Security.Claims and System.IdentityModel.Tokens.Jwt libraries are imported in the code

• Identifies calls to WriteToken() method that create JWT tokens

• Checks if the JWT security token passed to WriteToken() is created with potentially unsafe configurations or contains sensitive data

• Reports a vulnerability when WriteToken() is called with an unsafe JWT security token configuration

Vulnerable code example

using System.Security.Claims;
using System.IdentityModel.Tokens.Jwt;
using Microsoft.IdentityModel.Tokens;
using Microsoft.AspNetCore.Http;
using System.Text;

public class JwtHandler 
{...

✅ Secure code example

using System.Security.Claims;
using System.IdentityModel.Tokens.Jwt;
using Microsoft.IdentityModel.Tokens;
using Microsoft.AspNetCore.Http;
using System.Text;

public class JwtHandler 
{...