CVE-2025-27852: Garmin WDU Reflected XSS Vulnerability

CVE-2025-27852 Overview

CVE-2025-27852 is a reflected cross-site scripting (XSS) vulnerability affecting the locally served website on the Garmin Wireless Display Unit (WDU). The flaw impacts WDU v1 firmware 1.4.6 and WDU v2 firmware 5.0. An attacker on the same local network segment can craft a malicious URL that injects arbitrary JavaScript into the WDU web interface. Successful exploitation grants full administrator-level access to the device. Exploitation requires user interaction: the victim must view a specific URL served by the WDU and click an element on the rendered page.

Critical Impact

Successful exploitation yields full administrator-level access to the Garmin WDU, allowing attackers on the local network to take over the device through reflected JavaScript execution.

Affected Products

• Garmin WDU v1 firmware 1.4.6
• Garmin WDU v2 firmware 5.0
• Locally served WDU web interface

Discovery Timeline

• 2026-05-13 - CVE-2025-27852 published to the National Vulnerability Database (NVD)
• 2026-05-13 - Last updated in NVD database

Technical Details for CVE-2025-27852

Vulnerability Analysis

The Garmin WDU exposes a local web server that renders user-controllable input without proper output encoding. This results in a reflected XSS condition where attacker-supplied JavaScript is reflected back to the browser and executed in the context of the WDU webpage. Because the WDU web interface holds administrator privileges within the device, the executed script inherits those privileges and can perform any action the administrator could perform through the interface.

Exploitation is a two-step interaction. First, the victim must load a specific attacker-crafted URL served by the WDU. Second, the victim must click an element on the rendered page to trigger the injected payload. The attacker must reside on the same local network segment to reach the WDU's HTTP service.

Root Cause

The root cause is improper neutralization of input during web page generation in the WDU's local web application. Input parameters supplied through the URL are echoed into the response HTML without contextual encoding, allowing <script> content or event-handler attributes to execute when rendered by the victim's browser.

Attack Vector

The attack vector is adjacent network access combined with user interaction. An attacker who can reach the WDU on the local network segment delivers a malicious link to a user authenticated to the WDU. Once the user opens the link and performs the required click, the script runs in the WDU origin and can issue administrative API calls, change configuration, or pivot to other resources accessible from the WDU. Refer to the Garmin Support Page for product details.

Detection Methods for CVE-2025-27852

Indicators of Compromise

• HTTP requests to the WDU web interface containing <script>, onerror=, onclick=, or URL-encoded equivalents in query parameters
• Unexpected administrative configuration changes on the WDU originating from a legitimate user session
• Outbound HTTP requests from clients of the WDU web interface to unknown external hosts shortly after loading a WDU URL

Detection Strategies

• Inspect HTTP traffic to and from the WDU on the local network segment for reflected parameter values matching script payload signatures
• Correlate browser-side JavaScript errors or content security policy violations with access to WDU URLs
• Review WDU audit logs for administrative actions that do not align with normal operator workflows

Monitoring Recommendations

• Enable network packet capture or IDS coverage on the VLAN that hosts the WDU to flag XSS payload patterns in HTTP GET parameters
• Alert on first-seen URLs accessed against the WDU web server by any host other than expected operator workstations
• Monitor for repeated short-lived sessions to the WDU that include reflected parameters in the request URI

How to Mitigate CVE-2025-27852

Immediate Actions Required

• Restrict network access to the Garmin WDU web interface to trusted operator workstations using VLAN segmentation or host-based firewall rules
• Instruct operators to avoid clicking unsolicited links targeting the WDU web interface, especially links received from chat, email, or untrusted local sources
• Log out of the WDU web interface when not actively in use to reduce the window where reflected XSS can leverage an authenticated session

Patch Information

Review vendor guidance on the Garmin Support Page and the Garmin Official Website for firmware updates addressing the reflected XSS in WDU v1 1.4.6 and WDU v2 5.0. Apply firmware updates as soon as they are made available by Garmin for the affected models.

Workarounds

• Place the WDU on an isolated management network segment with no general user device access
• Use a dedicated browser profile or workstation to access the WDU web interface and avoid browsing other content from that session
• Block known reflected XSS payload patterns at any intermediate web application firewall protecting the WDU management network