CVE-2025-4347: D-Link DIR-600L Buffer Overflow Vulnerability

CVE-2025-4347 Overview

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

Critical Impact

This buffer overflow vulnerability in end-of-life D-Link DIR-600L routers enables remote attackers to compromise network infrastructure devices that are no longer receiving security updates from the vendor.

Affected Products

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

Discovery Timeline

• 2025-05-06 - CVE-2025-4347 published to NVD
• 2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4347

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 formWlSiteSurvey function in the D-Link DIR-600L firmware fails to properly validate the size of user-supplied input in the host argument before copying it to a fixed-size buffer in memory.

When an attacker provides an oversized value for the host parameter, the function writes data beyond the allocated buffer boundaries, corrupting adjacent memory regions. This memory corruption can be leveraged to overwrite critical data structures, function pointers, or return addresses on the stack, potentially leading to arbitrary code execution with the privileges of the web server process running on the router.

The vulnerability is particularly concerning because the DIR-600L product line has reached end-of-life status and is no longer supported by D-Link, meaning affected devices will not receive security patches.

Root Cause

The root cause of CVE-2025-4347 is the lack of proper bounds checking in the formWlSiteSurvey function when processing the host argument. The vulnerable code copies user-controlled input into a fixed-size buffer without verifying that the input length does not exceed the buffer capacity. This is a classic buffer overflow condition resulting from unsafe string handling practices in the firmware's C code.

Attack Vector

The attack can be launched remotely over the network. An authenticated attacker with low privileges can send a specially crafted HTTP request to the router's web management interface targeting the formWlSiteSurvey function. By manipulating the host parameter with an oversized payload, the attacker triggers the buffer overflow condition.

The attack does not require user interaction and can be executed from any network position that has access to the router's administrative interface. Given that many consumer routers have their administrative interfaces accessible from the local network, any compromised device on the same network segment could potentially exploit this vulnerability.

Technical details and proof-of-concept information are available in the GitHub PoC Repository. Additional context can be found at VulDB #307465.

Detection Methods for CVE-2025-4347

Indicators of Compromise

• Unexpected crashes or reboots of the D-Link DIR-600L router
• Unusual network traffic patterns originating from the router device
• HTTP requests to the router's web interface containing abnormally long host parameter values
• Memory corruption signatures in router logs (if logging is enabled)

Detection Strategies

• Monitor HTTP traffic to router management interfaces for requests containing oversized parameters in formWlSiteSurvey endpoints
• Deploy network intrusion detection rules to identify buffer overflow attack patterns targeting D-Link devices
• Implement anomaly detection for unusual router behavior including unexpected restarts or configuration changes
• Review router access logs for suspicious administrative access attempts

Monitoring Recommendations

• Segment network traffic to isolate router management interfaces from general network access
• Configure SIEM rules to alert on repeated connection attempts to router administrative ports
• Monitor for firmware modification attempts or unauthorized configuration changes on D-Link devices

How to Mitigate CVE-2025-4347

Immediate Actions Required

• Identify all D-Link DIR-600L devices on your network and assess their exposure
• Disable remote management interfaces on affected routers immediately
• Restrict access to the router's web management interface to trusted IP addresses only
• Plan for immediate replacement of end-of-life DIR-600L devices with supported hardware

Patch Information

This vulnerability affects D-Link DIR-600L routers which have reached end-of-life status. D-Link is no longer providing security updates for this product line. As no patch will be released, the only effective remediation is to replace affected devices with currently supported router hardware.

For more information, visit the D-Link Official Website.

Workarounds

• Disable the web management interface entirely if remote administration is not required
• Implement strong firewall rules to block external access to router management ports (typically 80, 443, 8080)
• Place affected routers behind a separate firewall or network segment with strict access controls
• Consider deploying a VPN solution to secure any necessary remote administrative access

# Example iptables rules to restrict router management access
# Apply these rules on an upstream firewall protecting the vulnerable device

# Block external access to router management interface
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT