CVE-2024-9266

What it actually does

An attacker can supply a crafted URL to the Express Response object's redirect method, causing the application to redirect users to an arbitrary untrusted destination without validation.

Why it matters to the business

Users may be sent to phishing or malicious sites, eroding customer trust, enabling credential theft, and increasing downstream security incidents.

How an attack unfolds

An attacker identifies an Express endpoint that passes user-supplied data into res.redirect, crafts a link containing a malicious target URL, and lures victims to click it, resulting in redirection to attacker-controlled content.

How to fix it

Upgrade Express from versions 3.4.5 through 3.x to version 4.0.0 or later; implement a whitelist of allowed redirect targets in application code.

How to confirm the fix worked

Confirm the installed Express version is 4.0.0 or higher; review source for any remaining direct use of user input in res.redirect and test that only whitelisted domains are accepted.

Typical attack path

1. Locate Express application routes that invoke res.redirect with unsanitized input
2. Construct a request parameter that points the redirect to an external attacker domain
3. Distribute the crafted link via email, social media, or other channels
4. Victim browser follows the redirect to the malicious site

How to detect it

Inspect web server and application logs for redirect responses containing external domains not present in the application's normal allowlist; correlate with user-agent and referrer fields for suspicious patterns.

What your security team should do

• Upgrade all instances of Express to 4.0.0 or later immediately
• Add server-side validation enforcing an allowlist for redirect destinations
• Audit logs for redirects to external domains outside the organization's control