Summary

ApostropheCMS's password reset flow constructs the reset URL using req.hostname,
which is derived directly from the attacker-controlled HTTP Host header when
apos.baseUrl is not explicitly configured. An unauthenticated attacker who knows
a victim's email address can send a crafted reset request that causes the application
to email the victim a reset link pointing to the attacker's domain. When the victim
clicks the link, the valid reset token is delivered to the attacker, enabling full
account takeover.

Affected Component

modules/@apostrophecms/login/index.js — resetRequest route
Precondition: passwordReset: true is set and apos.baseUrl is not configured.

Vulnerability Details

The setPrefixUrls middleware (i18n layer) builds req.baseUrl using req.hostname:

// Simplified from i18n middleware
req.baseUrl = `${req.protocol}://${req.hostname}`;
req.absoluteUrl = req.baseUrl + req.url;

The resetRequest handler then passes this tainted value directly into URL construction:

const parsed = new URL(
  req.absoluteUrl,           // ← tainted by attacker's Host header
  self.apos.baseUrl
    ? undefined
    : `${req.protocol}://${req.hostname}${port}`  // ← also tainted
);
parsed.pathname = '/login';
parsed.searchParams.append('reset', reset);   // real, valid token
parsed.searchParams.append('email', user.email);
await self.email(..., { url: parsed.toString() }, ...);
// Email sent to victim with URL pointing to attacker-controlled domain

When apos.baseUrl is configured, it is used unconditionally and the attacker's
Host header is ignored — that path is not vulnerable.

Attack Scenario

1. Attacker identifies a valid user email (e.g. from the site's public interface).
2. Attacker sends:

   POST /api/v1/login/reset-request
   Host: evil.attacker.com
   Content-Type: application/json

   {"email": "victim@example.com"}

3. The application emails the victim:

   Click here to reset your password:
   http://evil.attacker.com/login?reset=TOKEN&email=victim@example.com

4. Victim clicks the link; attacker's server captures TOKEN.
5. Attacker calls the real target's reset endpoint with the captured token and
   sets a new password — full account takeover.

Preconditions

• passwordReset: true configured in login module options (opt-in)
• apos.baseUrl is not set (common in development and some production deployments)
• Attacker knows or can enumerate a valid account email

Impact

Full account takeover of any account whose email address is known to the attacker.
No authentication or interaction beyond sending a single HTTP request is required
from the attacker. The victim need only click a link in a legitimate-looking
password reset email from their own site.

Remediation

Operators (immediate): Always set apos.baseUrl in your configuration:

// app.js or module configuration
modules: {
  '@apostrophecms/express': {
    options: {
      baseUrl: 'https://yourdomain.com'
    }
  }
}

Framework fix (recommended): The resetRequest route should refuse to proceed
if apos.baseUrl is not configured, rather than falling back to the tainted
req.hostname. Example:

// In resetRequest handler
if (!self.apos.baseUrl) {
  throw self.apos.error(
    'invalid',
    'apos.baseUrl must be configured to enable password reset'
  );
}
const parsed = new URL(self.loginUrl(), self.apos.baseUrl);

This eliminates the attacker-controlled input entirely from the URL construction path.

References

• OWASP: Host Header Injection
• CWE-640: Weak Password Recovery Mechanism for Forgotten Password

References

• GHSA-gf43-24g3-5hw2