CVE-2025-15543: VX800v USB Information Disclosure Flaw

CVE-2025-15543 Overview

CVE-2025-15543 is a symlink attack vulnerability affecting TP-Link VX800v v1.0 devices. The flaw exists in the USB HTTP access path functionality where improper link resolution allows a crafted USB device to expose root filesystem contents. An attacker with physical access to the device can exploit this vulnerability to gain read-only access to sensitive system files, potentially exposing configuration data, credentials, and other critical information stored on the device.

Critical Impact

Physical attackers can leverage malicious USB devices to traverse the filesystem and read sensitive system files including configuration data, stored credentials, and network settings.

Affected Products

• TP-Link VX800v v1.0

Discovery Timeline

• 2026-01-29 - CVE CVE-2025-15543 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2025-15543

Vulnerability Analysis

This vulnerability is classified under CWE-59 (Improper Link Resolution Before File Access), commonly known as a symlink attack. The VX800v device implements an HTTP-based interface for accessing files on connected USB storage devices. However, this implementation fails to properly validate and resolve symbolic links before granting access to file contents.

The root cause lies in the device's failure to canonicalize file paths when processing USB HTTP access requests. When a malicious USB device containing specially crafted symbolic links is inserted, the device follows these links without proper boundary validation, allowing access outside the intended USB mount point and into the root filesystem.

Root Cause

The vulnerability stems from insufficient path validation in the USB HTTP access handler. The firmware does not verify whether resolved file paths remain within the expected USB mount directory boundaries after following symbolic links. This allows directory traversal via symlinks on the USB device that point to arbitrary locations on the root filesystem.

Attack Vector

Exploitation requires physical access to the target device. An attacker must:

1. Create a malicious USB storage device containing symbolic links pointing to sensitive filesystem locations (e.g., /etc/passwd, /etc/shadow, configuration files)
2. Insert the crafted USB device into the VX800v router
3. Access the USB HTTP interface to request files through the malicious symbolic links
4. The device follows the symlinks and serves content from the root filesystem

The attacker gains read-only access to any files readable by the HTTP service process, which typically runs with elevated privileges on embedded devices. This can expose network configurations, stored credentials, encryption keys, and firmware internals.

Detection Methods for CVE-2025-15543

Indicators of Compromise

• Unusual USB device activity or repeated USB insertions on VX800v devices
• HTTP access logs showing requests for system file paths through the USB interface
• Evidence of USB storage devices with suspicious symbolic link structures
• Unexplained access to the device's USB HTTP interface from unexpected locations

Detection Strategies

• Monitor and audit physical access to VX800v devices, particularly USB port access
• Review HTTP access logs for suspicious file access patterns through the USB interface
• Implement network monitoring to detect data exfiltration from the device
• Deploy endpoint monitoring solutions on networks where VX800v devices are present

Monitoring Recommendations

• Enable logging on VX800v devices if supported and review for anomalous USB activity
• Implement physical security controls around network infrastructure devices
• Monitor network traffic from VX800v devices for unusual data transfers
• Establish baseline behavior for device USB port usage to identify deviations

How to Mitigate CVE-2025-15543

Immediate Actions Required

• Restrict physical access to VX800v devices to authorized personnel only
• Disable USB functionality on VX800v devices if not required for operations
• Update to the latest firmware version from TP-Link when a patch becomes available
• Review device placement to ensure they are in physically secure locations

Patch Information

TP-Link has published firmware updates and support documentation. Administrators should check the TP-Link Firmware Download page for the latest available firmware for VX800v devices. Additional guidance is available in the TP-Link Support FAQ.

Workarounds

• Physically disable or block USB ports on VX800v devices if USB functionality is not required
• Implement physical access controls and monitoring for device locations
• Use network segmentation to limit potential exposure if a device is compromised
• Deploy security cameras or access logging for areas containing network infrastructure