CVE-2025-4342: D-Link DIR-600L Buffer Overflow Vulnerability

CVE-2025-4342 Overview

A critical buffer overflow vulnerability has been discovered in D-Link DIR-600L wireless routers running firmware versions up to 2.07B01. The vulnerability exists in the formEasySetupWizard3 function, where improper handling of the host argument allows an attacker to trigger a buffer overflow condition. This flaw can be exploited remotely over the network, potentially enabling an attacker to execute arbitrary code or cause a denial of service on affected devices.

This vulnerability is particularly concerning because it affects end-of-life products that are no longer receiving security updates from D-Link. Organizations and consumers still using these devices are at significant risk as no official patch will be released.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code or crash affected D-Link DIR-600L routers, with no vendor patch available for this end-of-life product.

Affected Products

• D-Link DIR-600L Firmware (up to version 2.07B01)
• D-Link DIR-600L Hardware

Discovery Timeline

• 2025-05-06 - CVE-2025-4342 published to NVD
• 2025-05-13 - Last updated in NVD database

Technical Details for CVE-2025-4342

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-120 (Buffer Copy without Checking Size of Input). The formEasySetupWizard3 function in the DIR-600L firmware fails to properly validate the length of the host argument before copying it into a fixed-size buffer. When an attacker supplies an overly long value for this parameter, it overflows the buffer boundary, potentially overwriting adjacent memory locations including return addresses or function pointers.

The network-accessible nature of this vulnerability makes it particularly dangerous. An attacker with low-level privileges on the network can remotely trigger the buffer overflow, potentially achieving complete device compromise. Given that router devices often serve as the gateway for entire networks, successful exploitation could allow attackers to intercept traffic, pivot to internal systems, or establish persistent access.

Root Cause

The root cause is insufficient input validation in the formEasySetupWizard3 function. The function copies user-supplied input from the host parameter into a fixed-size stack or heap buffer without verifying that the input length does not exceed the buffer's allocated size. This classic buffer overflow pattern occurs when developers use unsafe string copy functions or fail to implement proper bounds checking on user-controlled input.

Attack Vector

The attack can be launched remotely over the network. An attacker would craft a malicious HTTP request targeting the web management interface of the DIR-600L router, specifically invoking the formEasySetupWizard3 function with an oversized host parameter. The attacker requires low-level authentication or access to the router's management interface, which may be accessible from the local network or, if misconfigured, from the internet.

The exploitation flow involves:

1. Identifying a vulnerable D-Link DIR-600L router on the network
2. Sending a crafted HTTP request to the router's web interface
3. Including a malicious, oversized payload in the host parameter
4. The buffer overflow corrupts memory, potentially allowing code execution or causing device crash

Technical details and proof-of-concept information are available in the GitHub PoC Repository.

Detection Methods for CVE-2025-4342

Indicators of Compromise

• Unexpected reboots or crashes of DIR-600L routers indicating potential exploitation attempts
• Anomalous HTTP requests with unusually long parameter values targeting the router's web interface
• Network traffic patterns showing connections to the router's management port from unexpected sources
• Changes to router configuration or firmware that were not authorized by administrators

Detection Strategies

• Implement network monitoring to detect HTTP requests with abnormally long parameters (particularly in the host field) directed at D-Link router management interfaces
• Deploy intrusion detection/prevention systems (IDS/IPS) with signatures for buffer overflow attacks against embedded devices
• Monitor for unusual outbound connections from router IP addresses that could indicate compromise
• Enable logging on network firewalls to capture and analyze traffic to router management interfaces

Monitoring Recommendations

• Configure alerts for any access attempts to DIR-600L management interfaces from external networks
• Implement network segmentation monitoring to detect lateral movement if a router is compromised
• Regularly review access logs for the router management interface for suspicious patterns
• Monitor for firmware version changes or unexpected configuration modifications

How to Mitigate CVE-2025-4342

Immediate Actions Required

• Replace affected D-Link DIR-600L routers with currently supported models that receive security updates
• If immediate replacement is not possible, isolate affected devices from untrusted networks
• Disable remote management access to the router's web interface from external networks
• Implement strict network segmentation to limit exposure of vulnerable devices
• Monitor affected devices closely for signs of compromise until replacement can occur

Patch Information

No official patch is available for this vulnerability. D-Link has designated the DIR-600L as end-of-life, meaning the product no longer receives security updates or support. D-Link's standard guidance for end-of-life products is to retire and replace them with current models. For more information, visit the D-Link Official Website.

Additional vulnerability details can be found at VulDB #307460.

Workarounds

• Restrict access to the router's management interface to trusted IP addresses only using access control lists
• Disable the web-based setup wizard functionality if possible through advanced configuration
• Place the vulnerable router behind a properly configured firewall that filters malicious requests
• Use a VPN for any remote management needs rather than exposing the management interface directly
• Consider deploying a secondary firewall or security appliance in front of the vulnerable device

# Example: Block external access to router management interface
# Add firewall rule to restrict access to management port (adjust port number as needed)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

# Example: Log suspicious requests for analysis
iptables -A INPUT -p tcp --dport 80 -j LOG --log-prefix "ROUTER_ACCESS: "