High-Severity WatchGuard Agent Flaws Grant Full SYSTEM Privileges on Windows

WatchGuard has released a critical security update for its Windows-based agent software to remediate a series of vulnerabilities that could allow attackers to seize total control of a local system. The advisory highlights four distinct flaws, including a “chained” attack vector that enables a standard user to escalate their privileges to the highest level—NT AUTHORITY\SYSTEM.

The vulnerabilities impact the WatchGuard Agent on Windows, a core component used for endpoint management and security orchestration.

The most severe threat involves two high-impact vulnerabilities, CVE-2026-6787 and CVE-2026-6788. Researchers discovered that by “chaining” these agent service vulnerabilities together, a local attacker could bypass standard security boundaries to achieve a full system takeover.

Additionally, CVE-2026-41288 targets the agent’s patch management component. Due to an “incorrect permission assignment for a resource,” an authenticated local user can manipulate the service to elevate their privileges to SYSTEM. This is particularly dangerous as it turns a tool meant for security updates into a vehicle for compromise.

The update also addresses two separate stack-based buffer overflow vulnerabilities—CVE-2026-41286 and CVE-2026-41287—within the WatchGuard Agent Discovery Service.

Unlike the privilege escalation flaws, these can be triggered by an unauthenticated attacker on the same local network. By sending “Overflow Buffers” to the discovery service, an actor can crash the agent service, resulting in a Denial of Service (DoS). While a crash may seem less severe than a takeover, it effectively blinds the security agent, potentially allowing other malicious activities to go unnoticed.

WatchGuard has confirmed that these vulnerabilities affect all versions of the WatchGuard Agent on Windows up to and including 1.25.02.0000.

Administrators are urged to deploy WatchGuard Agent version 1.25.03.0000 immediately to all Windows endpoints. There are no known workarounds that provide equivalent protection to the official patch.