CVE-2025-27850: Garmin WDU Path Traversal Vulnerability

CVE-2025-27850 Overview

CVE-2025-27850 is a symlink attack vulnerability affecting the locally served web site on the Garmin Wireless Display Unit (WDU). The flaw exists in firmware versions v1 1.4.6 and v2 5.0. An attacker who uploads a malicious graphics package containing symbolic links can cause the embedded web server to follow those links when serving content. The server does not restrict symlink targets to a specific area of the filesystem. This allows retrieval of arbitrary files from the device, exposing sensitive configuration data and credentials stored on the WDU.

Critical Impact

Attackers with the ability to upload graphics packages can read arbitrary files from affected Garmin WDU devices, leading to information disclosure of sensitive system data.

Affected Products

• Garmin WDU v1 firmware version 1.4.6
• Garmin WDU v2 firmware version 5.0
• Locally served web interface on Garmin Wireless Display Unit

Discovery Timeline

• 2026-05-13 - CVE-2025-27850 published to NVD
• 2026-05-13 - Last updated in NVD database

Technical Details for CVE-2025-27850

Vulnerability Analysis

The vulnerability resides in the locally served web site on the Garmin WDU. The web server processes uploaded graphics packages and serves their contents to clients. When a package contains symbolic links, the server resolves those links during request handling. No filesystem sandboxing or chroot-style isolation constrains the resolution path. As a result, a symlink pointing outside the intended graphics directory causes the server to return file contents from arbitrary locations on the device filesystem.

Root Cause

The root cause is missing validation of symbolic link targets within uploaded archives. The web server treats symlinks as transparent indirections and follows them without verifying that the resolved path remains within an allowed directory. This is a classic symlink-following flaw [CWE-59] where the application fails to enforce a containment boundary on resolved filesystem paths.

Attack Vector

An attacker crafts a graphics package archive that includes symbolic links pointing to sensitive files on the target device, such as configuration files, credential stores, or system binaries. The attacker uploads the package through the WDU's graphics upload mechanism. When the local web server later serves the package contents, it dereferences the symlinks and returns the targeted file contents to the requester. The vulnerability requires the ability to upload graphics packages and access the local web interface.

No verified proof-of-concept code is available. Refer to the Garmin Product Support Page for vendor guidance.

Detection Methods for CVE-2025-27850

Indicators of Compromise

• Graphics package uploads containing symbolic link entries within archive metadata
• Web server access logs showing requests for files outside the expected graphics directory tree
• Unexpected file content returned from URLs that should map to graphics assets

Detection Strategies

• Inspect uploaded archives for symlink entries before extraction using tools that can enumerate archive metadata
• Monitor the WDU local web server for HTTP responses serving non-image content from graphics endpoints
• Audit firmware-level filesystem activity for reads outside the designated graphics package directory

Monitoring Recommendations

• Log all graphics package upload events and retain the original archive for forensic review
• Alert on access to the WDU web interface from unexpected client addresses on the local network
• Review network segmentation around devices that interface with the Garmin WDU to identify exposure paths

How to Mitigate CVE-2025-27850

Immediate Actions Required

• Restrict network access to the Garmin WDU local web interface to trusted operators only
• Disallow uploads of graphics packages from untrusted sources until firmware is updated
• Contact Garmin support to confirm availability of patched firmware for affected WDU versions

Patch Information

No specific patch identifier is published in the CVE record at this time. Consult the Garmin Corporate Website and the Garmin Product Support Page for firmware updates addressing CVE-2025-27850.

Workarounds

• Inspect graphics packages for symbolic links before uploading them to the device and reject any archive that contains symlink entries
• Isolate the WDU on a dedicated network segment that prevents unauthorized devices from reaching the web interface
• Limit physical and logical access to the upload mechanism to authorized personnel only

# Inspect a graphics package archive for symbolic link entries before upload
unzip -l graphics_package.zip | grep -i symlink
tar -tvf graphics_package.tar | awk '$1 ~ /^l/ {print}'