CVE-2025-4346: D-Link DIR-600L Buffer Overflow Flaw

CVE-2025-4346 Overview

A critical buffer overflow vulnerability has been identified in D-Link DIR-600L wireless routers running firmware versions up to 2.07B01. The vulnerability exists in the formSetWAN_Wizard534 function, where improper handling of the host argument allows remote attackers to trigger a buffer overflow condition. This vulnerability is particularly concerning as it affects end-of-life products that are no longer receiving security updates from D-Link.

Critical Impact

Remote attackers can exploit this buffer overflow to potentially execute arbitrary code or cause denial of service on affected D-Link DIR-600L routers. The device is end-of-life and will not receive vendor patches.

Affected Products

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

Discovery Timeline

• 2025-05-06 - CVE-2025-4346 published to NVD
• 2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4346

Vulnerability Analysis

This vulnerability is a classic buffer overflow (CWE-120) resulting from improper restriction of operations within memory buffer bounds (CWE-119). The formSetWAN_Wizard534 function in the D-Link DIR-600L firmware fails to properly validate the length of user-supplied input passed through the host argument before copying it into a fixed-size memory buffer.

When an attacker sends a specially crafted request with an oversized host parameter, the function writes data beyond the allocated buffer boundary. This memory corruption can overwrite adjacent memory structures, including return addresses on the stack, potentially allowing an attacker to hijack program execution flow.

The vulnerability is remotely exploitable over the network without requiring physical access to the device, making it accessible to any attacker who can reach the router's web management interface.

Root Cause

The root cause lies in insufficient bounds checking within the formSetWAN_Wizard534 function. The firmware code fails to validate or sanitize the length of the host parameter before processing it. Without proper input length verification, the function copies user-controlled data into a stack or heap buffer without ensuring the destination buffer can accommodate the input, leading to a buffer overflow condition.

Attack Vector

The attack can be executed remotely over the network by sending malicious HTTP requests to the router's web management interface. An authenticated attacker with low privileges can exploit this vulnerability by:

1. Accessing the router's web management interface
2. Sending a crafted request to the vulnerable formSetWAN_Wizard534 endpoint
3. Including an oversized payload in the host parameter
4. Triggering the buffer overflow to corrupt memory

The vulnerability mechanism involves sending HTTP requests with oversized host parameter values to the formSetWAN_Wizard534 function endpoint. The lack of input validation allows the attacker-controlled data to overflow the designated buffer. Technical details and proof-of-concept information can be found in the GitHub PoC Repository.

Detection Methods for CVE-2025-4346

Indicators of Compromise

• Abnormal HTTP POST requests targeting the WAN wizard configuration endpoints with unusually large parameter values
• Unexpected router reboots or service crashes that may indicate exploitation attempts
• Unusual network traffic patterns originating from the router's management interface
• Memory corruption errors or system instability in router logs

Detection Strategies

• Monitor HTTP traffic to D-Link DIR-600L devices for requests containing abnormally long host parameters
• Implement network intrusion detection rules to identify buffer overflow patterns in router management traffic
• Deploy network segmentation to isolate vulnerable IoT devices from critical network segments
• Use web application firewalls to filter requests with suspicious payload sizes targeting the management interface

Monitoring Recommendations

• Enable logging on network firewalls to track access attempts to D-Link router management interfaces
• Configure SIEM alerts for unusual traffic patterns targeting port 80/443 on known D-Link DIR-600L devices
• Regularly audit network inventory to identify and track all end-of-life D-Link devices
• Monitor for any unauthorized configuration changes on affected routers

How to Mitigate CVE-2025-4346

Immediate Actions Required

• Immediately restrict remote access to the router's web management interface by disabling remote management features
• Implement network-level access controls to limit management interface access to trusted IP addresses only
• Place affected routers behind a firewall that blocks external access to the management interface
• Plan for immediate replacement of affected end-of-life devices with currently supported alternatives

Patch Information

No patch is available. D-Link has discontinued support for the DIR-600L router, and no security update will be released to address this vulnerability. Organizations and individuals using this device must implement workarounds or replace the affected hardware with a supported product.

For additional information, refer to the VulDB entry #307464 and the D-Link Official Website for supported device recommendations.

Workarounds

• Disable remote management entirely and only manage the device from a physically connected machine
• Implement strict firewall rules to block external access to the router's management ports (typically TCP 80 and 443)
• Use a VPN or jump host for any necessary remote administration rather than exposing the management interface directly
• Replace the end-of-life DIR-600L with a currently supported router model that receives security updates

# Example iptables rules to restrict management interface access
# Block external access to router management interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

# Log blocked access attempts for monitoring
iptables -A INPUT -p tcp --dport 80 -j LOG --log-prefix "DIR600L-MGMT-BLOCKED: "
iptables -A INPUT -p tcp --dport 443 -j LOG --log-prefix "DIR600L-MGMT-BLOCKED: "