Email Injection in Adonisjs with Dynamodb

Email injection occurs when user-controlled input is improperly handled in email-related operations, allowing an attacker to inject additional headers or commands. In an AdonisJS application using DynamoDB as the persistence layer, the risk arises at the intersection of AdonisJS request handling and the way data is stored and retrieved from DynamoDB.

AdonisJS does not inherently sanitize email inputs used in mailer configurations or user registration flows. If a developer directly uses user-supplied values—such as email or username—when writing items to DynamoDB, the raw input is persisted without validation. Later, when the application retrieves the item (for example during account confirmation or password reset) and passes the stored value to an email transport (SMTP or an API-based service), the injected content can alter message routing or header structure.

Because DynamoDB is a NoSQL database, schema flexibility means there are no built-in constraints to prevent storing newline characters or special sequences in string attributes. An attacker can submit an email like attacker@example.com\r\nCC: victim@example.com, which is accepted and stored as-is. When the application later reads the item and uses the value in an email header, the injected newline and CC line can cause the message to be sent to unintended recipients, a classic mail header injection pattern aligned with OWASP API Top 10:2023 A03 – Injection.

In a typical AdonisJS + DynamoDB flow, the application might use the AWS SDK for JavaScript to perform PutItem and GetItem operations. If input validation is limited to presence checks and type checks (e.g., ensuring the field is a string), newline and carriage return characters will pass through. DynamoDB stores them as plain text, and the vulnerability becomes latent until the data is used in an email context. This creates a pipeline where persistence and transport layers combine to amplify the impact of a simple injection flaw.

Real-world exploit patterns include using Bcc: to silently copy messages, adding extra Reply-To: addresses to hijack responses, or injecting MIME boundary strings to break parsing. Because the DynamoDB scan and query operations return the raw stored values, any downstream usage in email generation must treat these values as untrusted. A scanner that checks API endpoints for injection vectors—such as the 12 parallel checks run by middleBrick—can surface these risks by correlating input validation gaps with data exposure findings across the authentication and property authorization checks.

To remediate email injection in an AdonisJS application using DynamoDB, enforce strict validation on email inputs before they are stored or used in mail operations. Treat data from DynamoDB as untrusted on retrieval, applying the same validation and encoding applied at input time.

1. Validate and sanitize on write: Use a robust email validation library and reject or normalize inputs containing unexpected control characters. For example, disallow newline and carriage return characters explicitly.

const validator = use('validator')
const email = request.input('email')

// Reject obviously malformed or dangerous input
if (!validator.isEmail(email) || email.includes('\n') || email.includes('\r')) {
  throw new Error('Invalid email format')
}

2. Use DynamoDB Document Client with parameterized commands to avoid accidental concatenation issues. When storing user data, ensure the email field is written as a validated string:

const AWS = require('aws-sdk')
const dynamoDb = new AWS.DynamoDB.DocumentClient()

await dynamoDb.put({
  TableName: 'users',
  Item: {
    userId: 'uuid-v4-here',
    email: validatedEmail, // already validated
    createdAt: new Date().toISOString()
  }
}).promise()

3. Sanitize on read before email usage: When retrieving items for email-related workflows, re-validate and encode the email value, especially if it might be used in headers or templates:

const result = await dynamoDb.get({
  TableName: 'users',
  Key: { userId: 'uuid-v4-here' }
}).promise()

const storedEmail = result.Item?.email
if (!storedEmail || !validator.isEmail(storedEmail) || storedEmail.includes('\n') || storedEmail.includes('\r')) {
  throw new Error('Invalid stored email')
}

// Use a dedicated mail library that escapes headers
await Mail.send('welcome', { email: storedEmail }, message => {
  message
    .to(storedEmail)
    .from('noreply@example.com')
    .subject('Welcome')
    // Avoid manually constructing headers with user input
})

4. Implement schema guidance in DynamoDB where possible: While DynamoDB does not enforce string patterns, you can document expected formats and use application-level checks. Combine this with AdonisJS schema validation for request bodies to ensure only well-formed emails reach DynamoDB.

5. Apply transport-layer safety: Configure your mail transporter to use strict header handling, avoiding manual header concatenation with user data. This reduces the chance that stored newline characters can alter routing even if a stray value persists.

By combining rigorous input validation, safe DynamoDB usage patterns, and cautious handling on retrieval, you mitigate the injection pathway across persistence and email transport boundaries.