# Email Header Injection

- ID: go-email-header-injection
- Severity: HIGH
- CWE: CWE-93 (CWE-93)
- Languages: Go
- Frameworks: go, gin, echo, fiber, chi

## Description

User input flows into email headers without CRLF validation.

## Detection Message

User input from {source} flows to email operation at {sink} without sanitization.
This can allow attackers to inject email headers via CRLF sequences.

## Remediation

Reject input containing CRLF characters and validate email addresses.

```go
func sanitizeHeader(s string) (string, error) {
    if strings.ContainsAny(s, "\r\n") {
        return "", errors.New("invalid characters")
    }
    return s, nil
}

subject, err := sanitizeHeader(r.FormValue("subject"))
if err != nil {
    http.Error(w, "Invalid input", 400)
    return
}
```

Learn more: https://shoulder.dev/learn/go/cwe-93/email-header-injection

## Documentation

[object Object]

## Related Rules

- **Email Header Injection** [HIGH]: 
- **Email Header Injection** [HIGH]: