CVE-2025-4343: D-Link DIR-600L Buffer Overflow Vulnerability

CVE-2025-4343 Overview

A critical buffer overflow vulnerability has been identified in D-Link DIR-600L wireless routers running firmware versions up to 2.07B01. This vulnerability affects the formEasySetupWizard function, where improper handling of the host argument allows remote attackers to trigger a buffer overflow condition. As a network-accessible vulnerability requiring low attack complexity, this flaw poses significant risk to organizations still operating these end-of-life devices.

Critical Impact

Remote attackers can exploit this buffer overflow to potentially execute arbitrary code, compromise device integrity, and gain unauthorized access to the network. The affected D-Link DIR-600L devices are no longer supported by the manufacturer, meaning no security patches will be released.

Affected Products

• D-Link DIR-600L Firmware (all versions up to 2.07B01)
• D-Link DIR-600L Hardware Device
• dlink:dir-600l_firmware

Discovery Timeline

• May 6, 2025 - CVE-2025-4343 published to NVD
• May 13, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4343

Vulnerability Analysis

This buffer overflow vulnerability resides in the formEasySetupWizard function of the D-Link DIR-600L router firmware. The function fails to properly validate the length of user-supplied input passed through the host argument before copying it into a fixed-size buffer. When an attacker supplies an overly long string, the data overflows the allocated buffer space, corrupting adjacent memory regions.

The 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), both indicating fundamental input validation failures in the firmware's memory handling routines.

Root Cause

The root cause stems from inadequate bounds checking in the formEasySetupWizard function. The firmware developers did not implement proper length validation when processing the host parameter, allowing arbitrary-length input to be copied into a stack or heap buffer without size verification. This classic buffer overflow pattern results from unsafe string handling functions that do not enforce destination buffer limits.

Attack Vector

The attack vector is network-based, allowing remote exploitation without physical access to the device. An attacker can craft malicious HTTP requests targeting the Easy Setup Wizard functionality, embedding an oversized host parameter value designed to overflow the vulnerable buffer. The attack requires low privileges and no user interaction, making it highly exploitable in real-world scenarios.

Successful exploitation could allow attackers to:

• Overwrite return addresses or function pointers to redirect code execution
• Inject and execute malicious shellcode on the router
• Gain full administrative control over the device
• Pivot to attack other devices on the internal network

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

Detection Methods for CVE-2025-4343

Indicators of Compromise

• Unusual HTTP POST requests to the Easy Setup Wizard endpoint with abnormally long host parameter values
• Router crashes, reboots, or instability following web interface access attempts
• Unexpected outbound connections from the router to unknown external IP addresses
• Modified router configuration or unauthorized administrative accounts

Detection Strategies

• Deploy network intrusion detection rules to identify HTTP requests with oversized host parameters targeting D-Link router administration interfaces
• Monitor for anomalous traffic patterns from router IP addresses indicating potential compromise
• Implement deep packet inspection on network segments containing vulnerable D-Link devices
• Configure SIEM alerts for repeated failed or suspicious authentication attempts against router management interfaces

Monitoring Recommendations

• Establish baseline network behavior for router devices and alert on deviations
• Enable logging on network firewalls to capture all traffic to and from affected D-Link devices
• Review router access logs for unauthorized configuration changes or access attempts
• Deploy network segmentation to isolate end-of-life devices from critical infrastructure

How to Mitigate CVE-2025-4343

Immediate Actions Required

• Replace D-Link DIR-600L devices with currently supported router models that receive security updates
• Immediately disable remote management and WAN-side access to the router administration interface
• Implement strict network segmentation to isolate vulnerable routers from sensitive network segments
• Deploy web application firewall rules to filter malicious requests targeting the affected functionality

Patch Information

No patch is available. The D-Link DIR-600L has reached end-of-life status and is no longer supported by D-Link. The manufacturer will not release security updates for this vulnerability. Organizations must plan for immediate device replacement to address this security risk. For more information, visit the D-Link Official Website.

Additional vulnerability details are available through VulDB #307462 and VulDB CTI.

Workarounds

• Disable the Easy Setup Wizard functionality if possible through router configuration
• Restrict access to the router management interface to specific trusted IP addresses only
• Place vulnerable routers behind a firewall that blocks external access to management ports
• Use VLANs to isolate traffic from devices behind the vulnerable router

# Example: Block external access to router management (on upstream firewall)
iptables -A INPUT -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A INPUT -p tcp --dport 443 -d <router_ip> -j DROP
# Allow only trusted management subnet
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -d <router_ip> -j ACCEPT