CVE-2026-6788: WatchGuard Agent Path Element Vulnerability

CVE-2026-6788 Overview

CVE-2026-6788 is an Uncontrolled Search Path Element vulnerability [CWE-427] in WatchGuard Agent on Windows. The flaw affects WatchGuard Agent versions before 1.25.03.0000 and allows local attackers to load malicious files through an insecurely defined search path. Successful exploitation can lead to local code execution in the context of the agent process, compromising confidentiality, integrity, and availability on the affected host.

Critical Impact

A local attacker with low privileges can place a malicious file in a directory referenced by the agent's search path, leading to code execution under the agent's privilege level.

Affected Products

• WatchGuard Agent on Windows versions prior to 1.25.03.0000

Discovery Timeline

• 2026-05-06 - CVE-2026-6788 published to NVD
• 2026-05-06 - Last updated in NVD database
• 2026 - WatchGuard publishes WatchGuard Security Advisory WGSA-2026-00013

Technical Details for CVE-2026-6788

Vulnerability Analysis

The vulnerability is classified as an Uncontrolled Search Path Element [CWE-427]. The WatchGuard Agent on Windows resolves a dependent file, such as a Dynamic Link Library (DLL) or executable, using a search path that includes directories writable by lower-privileged users. An attacker who places a crafted file with a matching name in one of these directories causes the agent to load the attacker-controlled file instead of the intended trusted binary.

The attack requires local access and low privileges. No user interaction is required once the malicious file is staged. When the agent process starts or reloads the affected module, the malicious payload executes in the agent's security context.

Root Cause

The root cause is improper control over the search path used to locate binaries or libraries at runtime. The agent does not enforce fully qualified paths or restrict the search order to trusted system directories. This allows a local user to influence which file the agent loads.

Attack Vector

The attack vector is local. An authenticated user with write access to a directory in the agent's search path stages a malicious DLL or executable. When the WatchGuard Agent loads the targeted dependency, Windows resolves the name to the attacker's file, executing arbitrary code with the privileges of the agent process. The vulnerability is described in WatchGuard Security Advisory WGSA-2026-00013.

No verified public proof-of-concept code is available. Refer to the vendor advisory for technical details on the affected components and load behavior.

Detection Methods for CVE-2026-6788

Indicators of Compromise

• Unexpected DLL or executable files appearing in directories referenced by the WatchGuard Agent process
• WatchGuard Agent processes loading modules from non-standard or user-writable paths
• Child processes spawned by the WatchGuard Agent that do not match expected behavior
• File creation events in WatchGuard installation or working directories from non-administrative accounts

Detection Strategies

• Monitor ImageLoad events for the WatchGuard Agent and alert on modules loaded from paths outside the official installation directory
• Hunt for write operations to directories in the agent's PATH resolution order performed by non-privileged users
• Compare hashes of loaded modules against the vendor-supplied baseline for version 1.25.03.0000 and earlier

Monitoring Recommendations

• Enable Windows Sysmon Event ID 7 (Image Loaded) and Event ID 11 (FileCreate) on hosts running the WatchGuard Agent
• Forward endpoint telemetry to a centralized SIEM and create rules for anomalous module loads by the agent
• Review scheduled tasks, services, and autoruns for new entries pointing to suspicious binaries near WatchGuard directories

How to Mitigate CVE-2026-6788

Immediate Actions Required

• Upgrade WatchGuard Agent on Windows to version 1.25.03.0000 or later on all affected endpoints
• Audit local administrator and standard user access to WatchGuard installation directories and any directory in the system PATH
• Inventory hosts running the WatchGuard Agent and prioritize patching of multi-user systems and servers

Patch Information

WatchGuard has released a fixed version. Apply WatchGuard Agent 1.25.03.0000 or later as documented in WatchGuard Security Advisory WGSA-2026-00013. The patch addresses the insecure search path resolution behavior described in [CWE-427].

Workarounds

• Restrict write permissions on directories included in the agent's search path so only administrators can modify them
• Remove unnecessary writable directories from the system PATH environment variable
• Apply application allowlisting policies, such as Windows Defender Application Control or AppLocker, to block unsigned binaries from loading into the agent process
• Limit interactive logon on systems running the agent to trusted administrative users until the patch is applied