Use After Free in Adonisjs with Dynamodb

Use After Free occurs when memory is deallocated but references to it remain, and those references are later accessed. In a Node.js runtime such as AdonisJS, this typically surfaces through asynchronous patterns where callbacks or promises retain references to objects that have logically been released. When integrating AdonisJS with AWS DynamoDB, the interaction between the ORM/ODM lifecycle and the low-level DynamoDB Document Client can create conditions where stale references are used after the associated data structures have been cleared or reused.

Consider an AdonisJS service that retrieves an item from DynamoDB, processes it, and then explicitly nullifies or reuses a container holding the raw response. If an in-flight async operation (e.g., a promise chain, an event emitter callback, or a scheduled job) still holds a reference to the original item or its nested properties, and that item contains sensitive or mutable fields, accessing those fields after the container has been logically freed can expose unexpected data or cause erratic behavior. This is exacerbated by DynamoDB’s attribute structure, where nested maps and lists are deserialized into complex JavaScript objects that may retain internal references across request cycles in long-running processes.

Another common pattern in AdonisJS involves model hooks or middleware that attach DynamoDB response data to the model instance. If the model instance is recycled (for example, in an object pool or via a reused request context) while an asynchronous listener still references a property that was backed by a DynamoDB attribute, the listener might read or modify data that has already been logically released. This is effectively a Use After Free: the runtime memory may not be freed in the traditional systems sense, but the logical ownership of the data has been dropped, leading to information leaks or unstable state when the stale reference is used.

The DynamoDB Document Client performs automatic marshaling between JavaScript objects and DynamoDB’s attribute values. If an AdonisJS controller caches a Document Client response and later mutates or discards the controller’s local state without properly invalidating references, background tasks or subsequent request handling may inadvertently access cached properties that are no longer valid. For instance, a cached GetItem output might include an AWS SDK multipart buffer or a transformed Date object; if the controller replaces its reference but an in-flight async iterator still iterates over the old structure, sensitive fields like user identifiers or tokens could be exposed.

Real-world scenarios mapped to known attack patterns include:

• An authenticated route in AdonisJS calls DynamoDB to fetch a user profile, attaches the result to the request context, and schedules a background audit log task. If the request context is reused or cleared before the audit task completes, the task may read freed user data, potentially exposing PII or credentials.
• A GraphQL resolver in AdonisJS uses the DynamoDB Document Client to fetch nested configuration. If the resolver caches the raw document and later processes it in a microtask that executes after the resolver’s local variables have been cleared, stale references can lead to information disclosure or erratic validation logic.

These issues align with broader OWASP API Top 10 risks such as Security Misconfiguration and Excessive Data Exposure, especially when API responses include more data than necessary or retain internal references beyond their intended lifecycle. Instrumentation and strict lifecycle management are essential when using AdonisJS with DynamoDB to prevent Use After Free conditions.

To mitigate Use After Free when using AdonisJS with DynamoDB, focus on strict ownership semantics, explicit data copying, and lifecycle-aware async patterns. Avoid caching raw DynamoDB responses on long-lived contexts, and ensure that any asynchronous operation works on isolated copies rather than references to mutable state.

Below are concrete code examples for AdonisJS that demonstrate safe patterns when working with the AWS SDK v3 DynamoDB client.

1. Isolate responses with deep copies

Always create a fresh copy of DynamoDB output before attaching it to request-scoped or application-scoped objects. This prevents background tasks from accessing stale data.

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";

const ddb = new DynamoDBClient({});

async function getItemSafe(tableName, key) {
  const command = new GetItemCommand({ TableName: tableName, Key: marshall(key) });
  const { Item } = await ddb.send(command);
  // Create an isolated copy to avoid reference retention
  return JSON.parse(JSON.stringify(unmarshall(Item)));
}

2. Use request-local storage, not global caches

Store DynamoDB results in request-scoped containers (e.g., AdonisJS `ctx`) and clear references explicitly at the end of the request lifecycle.

import { HttpContextContract } from "@ioc:Adonis/Core/HttpContext";

export default class UserController {
  public async show({ params, response }: HttpContextContract) {
    const user = await getUserFromDynamo(params.id);
    // Attach to request context safely
    response.merge({ user });
    // Explicit cleanup if needed
    return response;
  }
}

3. Avoid reusing model instances across async boundaries

Do not attach DynamoDB-deserialized models to singletons or event emitters that may outlive the request. Instead, materialize plain objects for cross-boundary communication.

import { compose } from "@ioc:Adonis/Core/Helpers";

interface UserRecord {
  id: string;
  email: string;
  metadata: Record;
}

export function safeUserPayload(user: UserRecord) {
  // Return a plain object, not a class instance with hidden references
  return {
    id: user.id,
    email: user.email,
    metadata: { ...user.metadata },
  };
}

4. Control async lifetimes with cancellation tokens

When spawning background tasks that query DynamoDB, use cancellation or timeout patterns to ensure that tasks do not operate on data whose ownership has been released.

import { setTimeout as delay } from "timers/promises";

async function trackWithTimeout(taskId, timeoutMs = 5000) {
  try {
    await delay(timeoutMs);
    // Safe: runs in its own scope with copied inputs
    const status = await getTaskStatus(taskId);
    console.log(status);
  } catch (err) {
    // Handle timeout or cancellation
  }
}

5. Validate and limit exposure of DynamoDB attributes

Apply schema validation on unmarshalled items and return only necessary fields to reduce the impact of accidental reference use.

import { z } from "zod";

const UserSchema = z.object({
  id: z.string().uuid(),
  email: z.string().email(),
  createdAt: z.string().datetime(),
});

export function parseUserDynamo(attributes: Record) {
  const parsed = UserSchema.parse(attributes);
  return parsed;
}

Remediation checklist for AdonisJS + DynamoDB

• Never cache raw AWS SDK responses on long-lived objects.
• Use deep copies or schema validation when passing data across async boundaries.
• Prefer request-local storage for sensitive or mutable data.
• Explicitly clear references in hooks or middleware when objects are no longer needed.
• Instrument critical flows to detect unexpected cross-request data access.

These practices reduce the risk of Use After Free by ensuring that data ownership is clear, references are short-lived, and asynchronous operations work on isolated copies. They complement the scanning capabilities of tools like the middleBrick CLI, which can surface insecure patterns in API payloads and configurations when used as part of your CI/CD pipeline.