Critical WatchGuard Agent Vulnerabilities Grant SYSTEM Privileges on Windows

Key Takeaways

• WatchGuard has released critical security updates for its WatchGuard Agent on Windows.
• Multiple high-severity vulnerabilities, including local privilege escalation and denial-of-service flaws, have been identified.
• The most severe vulnerabilities allow authenticated local attackers to gain full SYSTEM privileges on affected machines.
• All versions of WatchGuard Agent on Windows up to and including 1.25.02.0000 are impacted.
• Immediate updates to version 1.25.03.0000 are crucial as no workarounds exist.

WatchGuard has issued urgent security patches to address several high-severity vulnerabilities present in its WatchGuard Agent software for Windows operating systems. These critical flaws could enable attackers to gain complete control over compromised systems or disrupt vital security services.

The most significant vulnerability chain permits authenticated local users to elevate their privileges to NT AUTHORITYSYSTEM, the highest possible access level on a Windows machine. Furthermore, other identified weaknesses include network-based buffer overflows that can lead to debilitating denial-of-service conditions.

Chained Local Privilege Escalation Exploits

Detailed in security advisory WGSA-2026-00013, two vulnerabilities, CVE-2026-6787 and CVE-2026-6788, pose a severe threat. These chained agent service vulnerabilities, affecting the Windows client, carry a CVSS score of 8.5, indicating their high severity.

Exploiting these flaws in sequence allows an attacker to execute a local privilege escalation, achieving NT AUTHORITYSYSTEM access. This level of compromise grants threat actors unrestricted capabilities, such as disabling security tools, deploying persistent malware, exfiltrating sensitive data, or creating covert administrative accounts.

Another significant privilege escalation vulnerability, CVE-2026-41288, holds a CVSS score of 7.3. This flaw originates from incorrect permission assignments within the WatchGuard Agent’s patch management component. An authenticated local user can leverage this misconfiguration to elevate their privileges from a standard user to SYSTEM level. This means even a low-privileged user account could completely compromise an endpoint device if the software remains unpatched.

Network-Based Denial of Service

In addition to the privilege escalation risks, WatchGuard engineers also resolved two stack-based buffer overflow vulnerabilities in the agent’s discovery service. These vulnerabilities, tracked as CVE-2026-41286 and CVE-2026-41287, each have a CVSS score of 7.1.

Unlike the privilege escalation flaws, which demand local access, these overflow vulnerabilities can be exploited by unauthenticated attackers on the same local network. By sending specially crafted requests, attackers can trigger memory buffer overflows, causing the agent service to crash. This results in a denial-of-service state, temporarily impairing the endpoint’s security management and monitoring capabilities and potentially opening the door for further network intrusions.

According to official WatchGuard advisories, all four vulnerabilities affect WatchGuard Agent on Windows versions up to and including 1.25.02.0000. WatchGuard has explicitly stated that no workarounds or mitigations exist beyond applying the official software update.

What You Should Do

• Immediately update all installations of WatchGuard Agent on Windows to version 1.25.03.0000.
• Verify that the update has been successfully applied across all endpoint environments.
• Monitor security logs for any suspicious activity that may indicate attempted exploitation of these vulnerabilities prior to patching.

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