GuardLapse: How a WatchGuard ‘Feature’ Became a Serious Security Vulnerability

Security features are meant to protect your network not put it at risk.

Recently, the GuardLapse WatchGuard Vulnerability has come to light as security researchers at ProjectBlack have turned the spotlight on WatchGuard’s “HTTP-Proxy: Detect Portal Authentication” setting, which behaves more like a vulnerability than a safeguard. Nicknamed GuardLapse, this issue shows how a well intentioned feature can leave organizations exposed to attack. Understanding this vulnerability is essential for maintaining network security and preventing potential breaches.

This post dives into what GuardLapse is, why it matters, and what steps you should take within the context of GuardLapse to protect your WatchGuard secured network.

What Is GuardLapse and How Does It Work?

GuardLapse refers to the HTTP-Proxy portal authentication detection feature found in WatchGuard Firebox appliances.

When enabled, this feature is supposed to detect captive portals and authentication pages. However, ProjectBlack’s research reveals that attackers can abuse it to bypass intended firewall protections.

By simply inserting a string like “/fgtauth” in a URL, a remote attacker can exploit the vulnerability to allow otherwise blocked traffic giving them direct access to internal web services, illustrating the vulnerability aspect of GuardLapse.

This is especially risky for organizations relying on WatchGuard, when faced with the vulnerability of GuardLapse, to segment critical services or block external access to sensitive systems.

Why Is GuardLapse Dangerous?

Bypasses Security Policies: Attackers can circumvent rules designed to block access to restricted apps or data, further exposing the vulnerability aspect within GuardLapse settings.
Hard to Detect: The exploit does not require advanced hacking skills or malware just manipulating URLs under the vulnerability conditions.
Exposes Internal Services: Threat actors could reach resources that should be protected, increasing the risk of data breaches or lateral movement inside your network.
Widespread Exposure: Many organizations are potentially affected by the vulnerability if the feature is enabled on their WatchGuard devices.

GuardLapse WatchGuard Vulnerability - How to Check and Mitigate GuardLapse

GuardLapse WatchGuard Vulnerability - Review Your Firebox Settings

Log in to your WatchGuard device to begin addressing the GuardLapse WatchGuard vulnerability.
Navigate to your HTTP-Proxy policy settings.
Look for the “Detect Portal Authentication” option and review its status.

GuardLapse WatchGuard Vulnerability - Disable the Feature If Not Needed

ProjectBlack recommends turning off this setting unless your environment specifically requires it for captive portal detection.

GuardLapse WatchGuard Vulnerability - Audit and Harden Access Policies

Ensure only authorized users have access to sensitive web apps.
Regularly test your firewall rules to confirm they work as intended against the vulnerability.