Attacking Password Resets with Host Header Injection

Summary

In this video, ipsec demonstrates the risk of password reset vulnerabilities caused by host header injection. By manipulating the host header in a password reset request, attackers can redirect the reset link to their own server and gain unauthorized access to user accounts. The video outlines testing methods using Burp Suite, real-world consequences like automated email filters, and offers prevention strategies such as whitelisting hostnames, using reverse proxies like Cloudflare, and validating host headers. The demonstration shows how misconfigurations can expose websites to this simple yet critical security flaw.

Takeaways

• 😀 Host header injection can be exploited in password reset functionality to redirect reset links to an attacker's server, enabling unauthorized access.
• 🔐 Burp Suite is an essential tool for testing and manipulating HTTP requests, making it easy to modify host headers and simulate attacks.
• ⚠️ If a website uses the host header for generating password reset links, it may be vulnerable to host header injection attacks if not properly validated.
• 💡 Cloudflare and other reverse proxies help protect against host header injections by acting as intermediaries and validating host headers before forwarding requests.
• 🔍 Mail filters that automatically click on links in emails can unknowingly expose sensitive reset tokens to attackers, making host header injections even more dangerous.
• 💥 Websites misconfigured behind services like Cloudflare can still be vulnerable if attackers discover the web server's IP address and bypass the proxy.
• 🔑 A whitelist approach should be used to ensure that only trusted domains are accepted in the host header during password reset processes.
• 🛡️ Using environment variables to store expected domains can help prevent unauthorized access by ensuring that only valid host headers are processed.
• 📜 Domain validation is critical—ensure the host header matches the expected domain to prevent manipulation through host header injection.
• ⚙️ Defense in depth is essential: relying on a single layer of security, like Cloudflare, is not enough—additional validation and checks should be applied.

Q & A

What is a password reset vulnerability involving host header injection?

A password reset vulnerability involving host header injection occurs when a web application generates a password reset link using the host header without validating or restricting it. If an attacker can manipulate the host header, they can alter the link, allowing them to reset the victim's password and gain unauthorized access.

Why is this vulnerability not as common in modern web applications?

This vulnerability is not as common because many modern web technologies, such as Cloudflare, use reverse proxies and perform checks on the host header. These technologies often prevent direct access to web servers, reducing the likelihood of exploitation.

How does a reverse proxy like Cloudflare protect against host header injection attacks?

Cloudflare acts as a reverse proxy and validates the host header to ensure it matches the expected domain. If the host header is tampered with, Cloudflare will prevent the request from reaching the web server, thus mitigating the risk of host header injection.

What is the role of a firewall in preventing this vulnerability?

A firewall can restrict access to a web server by only allowing trusted IP addresses or services, such as Cloudflare, to interact with it. This helps prevent attackers from bypassing reverse proxies and directly accessing the server, where they could exploit host header injection vulnerabilities.

What is the potential danger of automated email filters clicking on password reset links?

Automated email filters might click on password reset links without the user's knowledge, which can lead to exposing sensitive information, such as a reset token, to attackers. This can give attackers the ability to reset passwords and gain unauthorized access to accounts.

How did the attacker in the video demonstrate a successful host header injection exploit?

The attacker modified the host header in a request using Burp Suite to direct the request to their own IP address. This caused the application to send the password reset token to the attacker's server, granting them the ability to reset the victim's password.

What steps did the attacker take to capture the reset token?

The attacker intercepted the password reset request using Burp Suite, changed the host header to their IP address, and observed the password reset token being sent to their server. This allowed them to gain access to the reset link and potentially change the victim's password.

What methods can be used to protect a web application from host header injection attacks?

To protect against host header injection, web applications can implement a whitelist approach to verify the host header, use environment variables to set trusted domains, and employ reverse proxies like Cloudflare to prevent direct access to web servers. Additionally, using HTTPS and security libraries may further protect the application.

What is the whitelist approach to mitigating host header injection, and why is it effective?

The whitelist approach involves checking the host header against a list of trusted domains before processing any request. This ensures that only legitimate requests from expected domains can trigger actions like password resets, effectively preventing attackers from manipulating the host header.

What additional security measures were recommended to mitigate the risk of host header injection?

In addition to the whitelist approach, other recommended measures include using HTTPS to prevent man-in-the-middle attacks, implementing domain validation to check that the host header matches the expected domain, and utilizing reverse proxies like Cloudflare to obscure the web server's direct exposure to the internet.