Brute Force Attack in Nestjs

Brute force attacks in NestJS applications typically target authentication endpoints where attackers systematically attempt to guess valid credentials. In NestJS, this vulnerability manifests through several specific code patterns and architectural decisions that developers commonly implement.

The most common manifestation occurs in custom authentication guards and login controllers. Consider a typical NestJS login endpoint:

@Controller('auth')
export class AuthController {
  @Post('login')
  async login(@Body() credentials: LoginDto) {
    const user = await this.userService.findByEmail(credentials.email);
    if (!user) {
      throw new UnauthorizedException('Invalid credentials');
    }
    
    const isValid = await this.passwordService.compare(
      credentials.password,
      user.password
    );
    
    if (!isValid) {
      throw new UnauthorizedException('Invalid credentials');
    }
    
    return this.jwtService.sign({ userId: user.id });
  }
}

This implementation is vulnerable because it provides no rate limiting, no account lockout mechanism, and returns the same error response regardless of whether the email exists. Attackers can exploit this by making thousands of requests per minute, systematically trying common passwords or email/password combinations.

Another NestJS-specific manifestation occurs with JWT token generation. Many developers implement token refresh endpoints without proper throttling:

@Post('refresh')
async refresh(@Body() { refreshToken }) {
  // No rate limiting on refresh attempts
  const user = await this.validateRefreshToken(refreshToken);
  return { accessToken: this.jwtService.sign(user) };
}

Without rate limiting, attackers can continuously attempt to refresh tokens, potentially gaining access if they obtain a valid refresh token through other means.

NestJS applications also frequently expose GraphQL endpoints that are particularly vulnerable to brute force attacks. The flexible nature of GraphQL allows attackers to craft complex queries that can be executed repeatedly without traditional rate limiting:

@Resolver()
export class UserResolver {
  @Mutation()
  async login(@Args('input') input: LoginInput) {
    // No throttling on GraphQL mutations
    return this.authService.login(input);
  }
}

The issue compounds when developers use third-party authentication libraries or Passport strategies without understanding their default security configurations. Many NestJS applications integrate with OAuth providers, LDAP, or custom authentication systems where the default implementations lack proper brute force protections.

Detecting brute force vulnerabilities in NestJS applications requires both static code analysis and runtime monitoring. The most effective approach combines automated scanning with manual code review of authentication patterns.

middleBrick's API security scanner specifically targets NestJS authentication endpoints through black-box testing. The scanner identifies endpoints that accept authentication credentials and systematically tests for rate limiting deficiencies. When scanning a NestJS application, middleBrick examines:

Authentication Endpoint Discovery: The scanner automatically detects login, register, and refresh token endpoints by analyzing HTTP methods, paths, and parameter structures typical of NestJS applications.

Rate Limiting Assessment: middleBrick tests authentication endpoints by sending rapid sequential requests, measuring response times and server behavior to determine if rate limiting is implemented.

Error Response Analysis: The scanner analyzes error messages to identify whether the application leaks information about valid usernames or provides consistent timing that aids brute force attacks.

GraphQL Endpoint Testing: For applications using @nestjs/graphql, middleBrick specifically tests GraphQL mutations that handle authentication, as these often bypass traditional REST API protections.

Here's how you can use middleBrick to scan your NestJS API:

# Using the CLI tool
npm install -g middlebrick
middlebrick scan https://your-nestjs-api.com

# Or integrate into your CI/CD
middlebrick scan --url https://staging.your-nestjs-app.com --fail-below B

The scanner provides detailed findings including the specific endpoints vulnerable to brute force attacks, the severity level, and actionable remediation steps tailored to NestJS patterns.

Additionally, developers should implement monitoring for suspicious authentication patterns. NestJS applications can log authentication failures and use libraries like class-validator to implement basic input validation that makes brute force attacks more difficult:

import { IsEmail, MinLength } from 'class-validator';

export class LoginDto {
  @IsEmail()
  email: string;
  
  @MinLength(8)
  password: string;
}

While validation alone doesn't prevent brute force attacks, it ensures attackers must use valid email formats and minimum password lengths, reducing the attack surface.

Remediating brute force vulnerabilities in NestJS applications requires implementing multiple defensive layers. The most effective approach combines rate limiting, account lockout mechanisms, and proper error handling.

Rate Limiting with NestJS Middleware: Implement rate limiting using NestJS middleware or guards. The @nestjs/throttler package provides built-in support:

import { Module } from '@nestjs/common';
import { ThrottlerModule } from '@nestjs/throttler';

@Module({
  imports: [
    ThrottlerModule.forRoot({
      ttl: 60,           // Time to live in seconds
      limit: 5,          // Maximum requests
      ignoreUserAgents: [/bot|crawler/i], // Optional: ignore bots
    }),
  ],
})
export class AppModule {}

Apply the throttler to specific controllers or globally:

@Controller('auth')
@UseGuards(ThrottlerGuard)
export class AuthController {
  @Post('login')
  @Throttle(10, 900000) // 10 requests per 15 minutes
  async login(@Body() credentials: LoginDto) {
    // Authentication logic
  }
}

Account Lockout Implementation: Implement account lockout after multiple failed attempts. This requires tracking failed attempts in a database or cache:

import { Injectable, BadRequestException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { RedisCache } from 'cache-manager';

@Injectable()
export class AuthService {
  constructor(
    @InjectRepository(User)
    private usersRepository: Repository,
    @Inject('CACHE_MANAGER')
    private cacheManager: RedisCache,
  ) {}

  async login(credentials: LoginDto) {
    const cacheKey = `auth_failures:${credentials.email}`;
    const failures = await this.cacheManager.get(cacheKey) || 0;
    
    if (failures >= 5) {
      throw new BadRequestException('Account temporarily locked');
    }

    const user = await this.usersRepository.findOne({ email: credentials.email });
    if (!user || !(await this.comparePasswords(credentials.password, user.password))) {
      await this.cacheManager.set(cacheKey, failures + 1, { ttl: 300 });
      throw new BadRequestException('Invalid credentials');
    }

    // Reset failures on successful login
    await this.cacheManager.del(cacheKey);
    return this.createJwt(user);
  }
}

Consistent Error Responses: Ensure all authentication failures return identical responses to prevent username enumeration:

async login(credentials: LoginDto) {
  const user = await this.usersRepository.findOne({ email: credentials.email });
  
  // Always perform password comparison to ensure consistent timing
  const isValid = user && await this.comparePasswords(credentials.password, user.password);
  
  if (!isValid) {
    // Log the attempt for monitoring
    this.logger.warn(`Failed login attempt for email: ${credentials.email}`);
    throw new BadRequestException('Invalid credentials');
  }
  
  return this.createJwt(user);
}

GraphQL-Specific Protection: For GraphQL endpoints, implement resolver-level throttling:

import { UseGuards } from '@nestjs/common';
import { ThrottlerGuard } from '@nestjs/throttler';

@Resolver()
export class AuthResolver {
  @Mutation()
  @UseGuards(ThrottlerGuard)
  @Throttle(10, 900000)
  async login(@Args('input') input: LoginInput) {
    return this.authService.login(input);
  }
}

Monitoring and Alerting: Implement monitoring to detect brute force patterns. NestJS applications can use built-in logging with custom filters:

@Injectable()
export class AuthFailedGuard implements CanActivate {
  constructor(private logger: Logger) {}

  async canActivate(context: ExecutionContext): Promise {
    const request = context.switchToHttp().getRequest();
    const { email } = request.body;
    
    // Log failed attempts with rate limiting
    const key = `auth:${email}:${Date.now() / 1000 | 0}`;
    const attempts = await this.redis.incr(key);
    
    if (attempts > 100) {
      this.logger.warn(`Potential brute force attack detected for ${email}`);
      // Trigger alert or additional blocking
    }
    
    return true;
  }
}

These remediation strategies, when combined, create multiple layers of defense against brute force attacks in NestJS applications. The key is implementing rate limiting at the application level while also considering infrastructure-level protections like WAF rules or API gateway throttling.