Testing For Email Header Injection

---
name: testing-for-email-header-injection
description: Use when test web application email functionality for SMTP header injection
  vulnerabilities that allow attackers to inject additional email headers, modify
  recipients, and abuse contact forms for spam relay. Use when testing web application
  email functionality for smtp header injection vulnerabilities.
domain: cybersecurity
tags:
- email-injection
- smtp-injection
- crlf-injection
- header-injection
- spam-relay
- contact-form
- email-security
subdomain: web-application-security
version: '1.0'
author: oyi77
license: Apache-2.0
nist_csf:
- PR.PS-01
- ID.RA-01
- PR.DS-10
- DE.CM-01
category: cybersecurity
---

# Testing For Email Header Injection

## Overview

Cybersecurity skill for testing for email header injection. Follows industry best practices and security standards.

## When to Use

**Trigger phrases:**
- "testing for email header injection"
- "When testing contact forms, feedback forms, or "email a friend" functionality"
- "During assessment of password reset email functionality"
- "When testing newsletter subscription or notification email systems"

- When testing contact forms, feedback forms, or "email a friend" functionality
- During assessment of password reset email functionality
- When testing newsletter subscription or notification email systems
- During penetration testing of applications that send emails based on user input
- When auditing email-related API endpoints for header injection


## When NOT to Use

- When you lack proper authorization for testing
- For production systems without change management
- When the task requires legal or compliance expertise beyond technical scope


## Prerequisites
- Burp Suite for intercepting and modifying HTTP requests
- Understanding of SMTP protocol and email header structure
- Knowledge of CRLF injection techniques (\r\n sequences)
- Test email accounts for receiving injected emails
- Access to application features that trigger email sending
- SMTP server logs access for monitoring injection attempts

## Workflow

```python
# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def extract_iocs(text: str) -> dict:
    return {k: re.findall(v, text) for k, v in IOC_PATTERNS.items()}
```

1. **Reconnaissance** — Gather information about the target related to . Identify attack surface.
2. **Vulnerability Identification** — Enumerate potential  weaknesses using automated and manual techniques.
3. **Exploit Development/Selection** — Use email header injection to identify and test  vulnerabilities.
4. **Execution** — Execute the  test in a controlled manner with proper authorization.
5. **Post-Exploitation** — Document the impact and extent of successful exploitation.
6. **Reporting** — Write detailed findings with reproduction steps, impact assessment, and remediation guidance.

## Tools

- **email header injection** — Primary tool for this skill
- **Vulnerability Scanner** — Automated weakness identification
- **Exploitation Framework** — Controlled exploitation testing
- **Reporting Tool** — Findings documentation and tracking


## Process

1. **Design** — Define interface, identify patterns, plan implementation
1. **Implement** — Write code following existing conventions, add tests
1. **Verify** — Run tests, check integration, validate behavior

## Verification

- [ ] All  procedures executed completely and documented
- [ ] Findings validated against multiple data sources
- [ ] False positives identified and filtered
- [ ] Results documented with evidence and timestamps
- [ ] Recommendations provided with risk-based prioritization

## Anti-Rationalization Table

| Rationalization | Reality |
|---|---|
| "We are too small to be targeted" | Automated attacks target everyone. Size does not matter. |
| "Security slows us down" | A breach slows you down 100x more. Build security in from the start. |
| "We will fix it after launch" | Vulnerabilities in production are exploited within hours. Fix before deploy. |