Mail Command Injection

ID

php.mail_command_injection

Severity

critical

Resource

Injection

Language

Php

Tags

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

Description

Improper neutralization of CRLF sequences sent to an SMTP, POP3, or IMAP mail server ('Mail Injection').

Rationale

Mail Command Injection occurs when inputs used to construct mail commands or emails in applications are not properly sanitized or validated. This can allow an attacker to inject additional commands or manipulate mail parameters for malicious purposes, potentially compromising system integrity or confidentiality.

For example, consider the following PHP code snippet:

<?php
$to = $_POST['email'];
$subject = "Welcome!";
$message = "Hello, thank you for registering.";
$headers = "From: webmaster@example.com";
mail($to, $subject, $message, $headers);
?>

Remediation

To remediate Mail Command Injection vulnerabilities in applications, follow these practical steps:

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

  2. Use Mail API: Rather than constructing mail commands manually, utilize a Mail API for handling email operations. Mail APIs abstract the complexities of mail handling and reduces the risk of command injection by not relying on shell commands:

  3. 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.

  4. 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.

  5. 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 Command 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