CVE-2025-5105: TOZED ZLT W51 Use-After-Free Vulnerability

CVE-2025-5105 Overview

A critical vulnerability has been identified in TOZED ZLT W51 devices running firmware versions up to 1.4.2. The vulnerability affects the Service Port 7777 component and is classified as an improper clearing of heap memory before release (CWE-244). This memory safety issue can be exploited remotely without authentication, potentially allowing attackers to access sensitive information that remains in memory after deallocation.

Critical Impact

Remote attackers can exploit this vulnerability over the network to potentially access sensitive data remnants in heap memory, compromise device confidentiality, and affect system integrity on vulnerable TOZED ZLT W51 devices.

Affected Products

• TOZED ZLT W51 firmware version 1.4.2 and earlier
• TOZED ZLT W51 devices with Service Port 7777 exposed
• Network-accessible TOZED ZLT W51 router deployments

Discovery Timeline

• 2025-05-23 - CVE-2025-5105 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-5105

Vulnerability Analysis

This vulnerability stems from improper memory management practices within the TOZED ZLT W51 firmware. When heap memory is allocated and subsequently freed, the device fails to properly sanitize or clear the memory contents before releasing it back to the memory pool. This creates a situation where sensitive data—such as authentication credentials, session tokens, or other confidential information—may persist in freed memory regions.

The vulnerability is accessible via Service Port 7777, which suggests this is a network service that handles some form of device management or communication functionality. The lack of proper memory clearing before release means that subsequent memory allocations could potentially expose previously stored sensitive data to unauthorized parties.

Root Cause

The root cause is classified under CWE-244 (Improper Clearing of Heap Memory Before Release). This weakness occurs when the firmware fails to properly overwrite or sanitize heap memory contents before calling free() or equivalent memory deallocation functions. In embedded systems like the ZLT W51, this type of vulnerability is particularly concerning because memory resources are often reused quickly, and sensitive data like WiFi credentials, administrative passwords, or encryption keys may be exposed.

Attack Vector

The attack can be launched remotely over the network by targeting Service Port 7777 on vulnerable devices. An attacker with network access to the device can potentially:

1. Send specially crafted requests to the service on port 7777
2. Trigger memory allocation and deallocation sequences
3. Attempt to read memory regions that contain residual sensitive data
4. Extract confidential information that was not properly cleared from heap memory

The vulnerability requires no authentication and no user interaction, making it particularly dangerous for devices exposed to untrusted networks.

The exploitation mechanism involves sending requests to Service Port 7777 that trigger memory operations, followed by attempts to read the uncleared memory contents. Technical details and proof-of-concept code are available in the LeakyTozed GitHub Repository. The repository includes a specific proof-of-concept demonstration that illustrates the memory disclosure attack vector.

Detection Methods for CVE-2025-5105

Indicators of Compromise

• Unusual network traffic patterns directed at port 7777 on TOZED ZLT W51 devices
• Unexpected connection attempts from external IP addresses to Service Port 7777
• Anomalous memory consumption or behavior patterns on affected devices
• Evidence of data exfiltration attempts following port 7777 service interactions

Detection Strategies

• Deploy network intrusion detection rules to monitor traffic to port 7777 on known TOZED device IP addresses
• Implement firewall logging for all connections to Service Port 7777
• Use network segmentation to isolate IoT devices and monitor cross-segment traffic
• Configure SIEM alerts for repeated connection attempts to device management ports

Monitoring Recommendations

• Establish baseline network behavior for TOZED ZLT W51 devices and alert on deviations
• Monitor for reconnaissance scanning activity targeting port 7777 across the network
• Implement continuous vulnerability scanning for embedded devices and firmware versions
• Review device access logs periodically for unauthorized connection attempts

How to Mitigate CVE-2025-5105

Immediate Actions Required

• Block external access to Service Port 7777 on all TOZED ZLT W51 devices using firewall rules
• Isolate affected devices from untrusted networks and implement network segmentation
• Conduct an inventory of all TOZED ZLT W51 devices running firmware version 1.4.2 or earlier
• Monitor for vendor firmware updates and apply patches as soon as they become available
• Consider replacing vulnerable devices if no firmware update is forthcoming from the vendor

Patch Information

The vendor (TOZED) was contacted regarding this vulnerability but did not respond to the disclosure. As of the last update on 2026-04-15, no official patch has been released. Organizations should monitor the vendor's official channels and security bulletins such as VulDB entry #310082 for any future updates regarding patches or firmware updates.

Workarounds

• Implement strict firewall rules to block all inbound connections to port 7777 from untrusted networks
• Place TOZED ZLT W51 devices behind a VPN or secure gateway requiring authentication
• Disable Service Port 7777 if the functionality is not required for device operation
• Use network access control (NAC) to restrict which hosts can communicate with vulnerable devices

# Example iptables rule to block external access to port 7777
iptables -A INPUT -p tcp --dport 7777 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p udp --dport 7777 -s ! 192.168.1.0/24 -j DROP

# Restrict access to only management VLAN
iptables -A INPUT -p tcp --dport 7777 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 7777 -j DROP