Use After Free in Feathersjs with Basic Auth

Use After Free (UAF) in a Feathersjs service that uses Basic Authentication occurs when an application continues to use a resource after it has been deallocated or reused. In the context of Feathersjs, this typically manifests through object reuse patterns in authentication state, hooks, or service methods where references to sensitive data outlive the intended scope of the request.

When Basic Auth is used, credentials are often decoded from the Authorization header on each request and attached to the connection or service context for downstream handlers. If the implementation stores decoded credentials in a mutable object that is later modified or cleared without invalidating existing references, a UAF condition can arise. For example, consider a hook that caches user information in a request-scoped object and reuses that object across asynchronous steps. If the credentials object is deallocated or reassigned while an asynchronous operation still holds a reference, a subsequent request could observe stale data or trigger operations on the freed memory pattern, leading to information disclosure or unexpected behavior.

In Feathersjs, this risk is heightened when middleware or hooks rely on mutable shared state. An attacker may exploit timing differences between request handling to influence what data occupies a previously freed memory region. Although Feathersjs runs in a Node.js environment where direct memory management is abstracted, the logical equivalent of Use After Free exists when references to user context, decoded credentials, or parsed authentication objects are retained beyond the request lifecycle or reused across concurrent requests.

Specific scenarios include:

• Storing decoded Basic Auth credentials in a request context that is not properly isolated between invocations.
• Using connection pools or session objects where authentication state is overwritten without clearing previous references.
• Asynchronous hooks that capture authentication objects in closures and later operate on them after the authentication step has been logically cleared.

These patterns do not require direct memory manipulation but create logical conditions where data meant for one request is erroneously used in another, violating authentication boundaries. middleBrick detects such authentication and authorization misconfigurations as part of its BOLA/IDOR and Authentication checks, highlighting risky references in the authentication flow.

To mitigate Use After Free risks when using Basic Authentication in Feathersjs, ensure that authentication state is immutable within the request lifecycle and that no references are retained beyond the scope of a single request. The following patterns demonstrate secure handling of Basic Auth credentials.

First, decode credentials per-request without caching them in mutable request properties:

// services/auth/hooks.js
const { AuthenticationError } = require('@feathersjs/errors');
const basicAuth = require('basic-auth');

const authenticateBasic = context => {
  const req = context.params.raw ? context.params.raw.req : context.app.get('request');
  const user = basicAuth(req);
  if (!user || !user.name || !user.pass) {
    throw new AuthenticationError('Missing credentials');
  }
  // Immediately validate credentials and return a clean user object
  return validateCredentials(user.name, user.pass).then(validUser => {
    // Do not attach raw credentials to context
    context.params.user = { id: validUser.id, role: validUser.role };
    return context;
  });
};

module.exports = {
  before: { all: [authenticateBasic] }
};

Second, avoid storing authentication state in shared or mutable objects. Instead, pass only necessary, non-sensitive identifiers through the context:

// src/hooks/is-valid-user.js
module.exports = function isValidUser() {
  return async context => {
    const { user } = context.params;
    if (!user || !user.id) {
      throw new Error('Unauthorized');
    }
    // Fetch user from database without reusing auth credentials
    const fullUser = await context.app.service('users').get(user.id);
    context.params.currentUser = { id: fullUser.id, permissions: fullUser.permissions };
    return context;
  };
};

Third, ensure that any request-specific data is cleared after the response is sent. Feathersjs hooks should not rely on properties that persist across invocations:

// src/hooks/clear-sensitive.js
module.exports = function clearSensitiveData() {
  return context => {
    // Explicitly remove any temporary authentication references
    if (context.params._tempAuth) {
      delete context.params._tempAuth;
    }
    return context;
  };
};

Combine these hooks in your service configuration to enforce strict separation between authentication validation and business logic:

// in src/services/index.js
const authHook = require('./hooks/auth');
const validationHook = require('./hooks/is-valid-user');
const clearHook = require('./hooks/clear-sensitive');

app.use('/secure-data', {
  async find(params) {
    // Business logic here
    return [];
  },
  before: {
    all: [authHook, validationHook, clearHook]
  }
});

These practices align with middleBrick’s findings for Authentication and BOLA/IDOR checks, ensuring that decoded credentials are not inadvertently exposed or reused. The scanner can identify places where authentication objects are retained in shared contexts, guiding you toward a more secure implementation.