Mail Content Injection

ID

php.mail_content_injection

Severity

low

Resource

Injection

Language

Php

Tags

CWE:93, NIST.SP.800-53, OWASP:2021:A3, PCI-DSS:6.5.1

Description

Improper validation of the body (content) of an email ('Mail Content Injection').

Rationale

Mail Content Injection involves injecting unwanted or malicious content specifically into the body of the email or header fields via improper handling of user inputs. This can lead to modification of the message content or header fields.

The main focus of a content injection is the ability to alter the actual email body or to inject additional headers by exploiting the format of the input data.

Inserting newline characters into inputs that are used in the email header could inadvertently allow an attacker to insert additional headers or alter the email body.

For example, consider the following PHP code snippet:

<?php

require_once '/path/to/vendor/autoload.php';

// Create the Transport
$transport = (new Swift_SmtpTransport('smtp.example.org', 25))
  ->setUsername('your username')
  ->setPassword('your password')
;

// Create the Mailer using your created Transport
$mailer = new Swift_Mailer($transport);

$body = $_POST['body'];

// Create a message
$message = (new Swift_Message('Wonderful Subject'))
  ->setFrom(['john@doe.com' => 'John Doe'])
  ->setTo(['receiver@domain.org', 'other@domain.org' => 'A name'])
  ->setBody($body) // FLAW
  ;

// Send the message
$result = $mailer->send($message);

Remediation

To remediate Mail Content Injection vulnerabilities follow these practical steps:

  1. Input Validation and Sanitization: Rigorously validate user inputs. Ensure they conform to expected patterns and remove any potentially dangerous characters or sequences.

  2. Escape Shell Inputs: If executing mail-related shell commands is necessary, ensure all user inputs are correctly escaped to prevent injection. However, this is still risky and should be avoided if possible.

  3. Dependency Updates: Ensure that libraries and tools related to email handling in your application are up to date with the latest security patches and recommendations.

  4. Security Reviews and Automated Testing: Incorporate security reviews and SAST into your development lifecycle to identify and address Mail Command Injection vulnerabilities early.

By adopting these practices, you can mitigate the risk of Mail Content Injection in your applications and enhance the security posture of your email handling processes.

Configuration

The detector has the following configurable parameters:

  • sources, that indicates the source kinds to check.

  • neutralizations, that indicates the neutralization kinds to check.

Unless you need to change the default behavior, you typically do not need to configure this detector.

References