CVE-2025-27853 Overview
CVE-2025-27853 is an authentication bypass vulnerability affecting the Garmin Wireless Display Unit (WDU) versions v1 1.4.6 and v2 5.0. The locally served web interface performs authentication entirely within the client's browser. The WebSockets used to communicate with the WDU server do not enforce server-side authentication. An attacker with network access to the WDU can bypass all authentication mechanisms by directly invoking the remote APIs exposed over the WebSocket channel.
Critical Impact
Attackers on the local network can invoke privileged WDU APIs without credentials by communicating directly with the WebSocket endpoint, bypassing the browser-side authentication entirely.
Affected Products
- Garmin WDU v1, firmware version 1.4.6
- Garmin WDU v2, firmware version 5.0
- Garmin Wireless Display Unit (product reference 010-02642-00)
Discovery Timeline
- 2026-05-13 - CVE-2025-27853 published to NVD
- 2026-05-13 - Last updated in NVD database
Technical Details for CVE-2025-27853
Vulnerability Analysis
The Garmin WDU exposes a locally served web application for device management and configuration. The application uses WebSockets to communicate between the browser client and the WDU server. Authentication logic is implemented exclusively on the client side within the browser. The server accepts and processes WebSocket messages without validating that the sender has authenticated.
This design flaw means any client that can establish a WebSocket connection to the WDU server can issue API calls. The browser-based login form provides no actual security boundary. The vulnerability falls under [CWE-287] Improper Authentication and aligns with broken access control patterns common to IoT devices that rely on client-side controls.
Root Cause
The root cause is the placement of authentication logic on the client rather than on the server. The WDU's WebSocket handler does not require, validate, or enforce session tokens, credentials, or any other authentication artifact before executing requested operations. Authentication checks executed in JavaScript inside the browser can be skipped by simply not loading or executing that JavaScript.
Attack Vector
An attacker with network reachability to the WDU connects directly to the WebSocket endpoint using a custom client. The attacker then sends API messages in the same format the legitimate web application would send after login. Because the server does not differentiate between authenticated and unauthenticated WebSocket clients, all available remote APIs are accessible. No credentials, tokens, or user interaction are required.
No verified public exploit code is available. See the Garmin Support Page for vendor information.
Detection Methods for CVE-2025-27853
Indicators of Compromise
- Unexpected WebSocket connections to the WDU's local web service from hosts other than the operator's management workstation
- WDU configuration changes or command executions that do not correlate with operator login events in the browser UI
- Repeated WebSocket handshake requests from scripted user agents or non-browser clients
Detection Strategies
- Monitor network traffic on the WDU management VLAN for WebSocket upgrade requests (HTTP Upgrade: websocket) originating from unauthorized endpoints
- Inspect WebSocket frames for API method invocations occurring without a preceding authentication exchange in the same session
- Baseline normal management traffic patterns and alert on deviations such as off-hours API activity or connections from new MAC addresses
Monitoring Recommendations
- Log all inbound connections to the WDU web service at the upstream switch or firewall
- Capture and retain WebSocket traffic for forensic review if the WDU is reachable from broader network segments
- Alert on any direct IP connections to the WDU from devices outside an explicit allowlist
How to Mitigate CVE-2025-27853
Immediate Actions Required
- Isolate the Garmin WDU on a dedicated management network segment that is not reachable from general user networks or the internet
- Restrict access to the WDU's web and WebSocket ports using firewall or switch ACLs limited to known administrator workstations
- Disable the local web interface when it is not actively required for configuration
Patch Information
No patch information is referenced in the NVD entry at the time of publication. Operators should consult the Garmin Support Page for firmware updates addressing CVE-2025-27853 and apply any released firmware revisions that supersede v1 1.4.6 and v2 5.0.
Workarounds
- Place the WDU behind a network appliance that enforces authentication or mutual TLS before forwarding traffic to the device
- Apply strict layer-3 segmentation so only authorized management hosts can reach the WDU's listening ports
- Physically disconnect the WDU's network interface when remote management is not required
# Example firewall rule restricting WDU access to a single admin host
# (adjust interface, addresses, and port to the deployment)
iptables -A FORWARD -p tcp -s 10.10.5.20 -d 10.10.50.10 --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d 10.10.50.10 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
