CVE-2025-4441: D-Link DIR-605L Buffer Overflow Vulnerability

CVE-2025-4441 Overview

A critical buffer overflow vulnerability has been identified in the D-Link DIR-605L wireless router firmware version 2.13B01. The vulnerability exists within the formSetWAN_Wizard534 function, where improper handling of the curTime argument allows an attacker to trigger a buffer overflow condition. This flaw 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 affects an end-of-life product with no security patches available, leaving all deployed devices permanently vulnerable to remote exploitation.

Affected Products

• D-Link DIR-605L Firmware version 2.13B01
• D-Link DIR-605L Hardware (all revisions running vulnerable firmware)

Discovery Timeline

• 2025-05-08 - CVE-2025-4441 published to NVD
• 2025-05-13 - Last updated in NVD database

Technical Details for CVE-2025-4441

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 formSetWAN_Wizard534 function fails to properly validate the length of data passed through the curTime parameter before copying it into a fixed-size buffer. When an attacker supplies an oversized input value, the data overflows the allocated buffer space, corrupting adjacent memory regions.

The network-accessible nature of this vulnerability is particularly concerning as it requires no physical access to the device. An authenticated attacker with low privileges can remotely trigger the overflow, potentially gaining complete control over the device's execution flow. The impact includes potential compromise of confidentiality, integrity, and availability of the affected router.

Root Cause

The root cause is a classic buffer overflow condition resulting from insufficient input validation in the formSetWAN_Wizard534 function. The firmware does not perform adequate bounds checking on the curTime argument before using it in memory copy operations. This allows data to be written beyond the intended buffer boundaries, leading to memory corruption.

Attack Vector

The attack can be initiated remotely over the network against the router's web management interface. An attacker with low-level authentication to the device can craft a malicious HTTP request containing an oversized curTime parameter value. When the vulnerable formSetWAN_Wizard534 function processes this request, the buffer overflow occurs, potentially allowing the attacker to:

1. Overwrite critical memory structures including return addresses
2. Achieve arbitrary code execution with router-level privileges
3. Cause denial of service by crashing the device
4. Establish persistent backdoor access to the network

The vulnerability mechanism involves insufficient bounds checking on the curTime parameter within the WAN configuration wizard functionality. When exploited, the oversized input overwrites adjacent memory, which can include control flow data. Technical details and proof of concept information are available in the GitHub vulnerability repository.

Detection Methods for CVE-2025-4441

Indicators of Compromise

• Unexpected reboots or crashes of the DIR-605L router
• Anomalous HTTP POST requests to the web management interface containing unusually long curTime parameter values
• Suspicious outbound network connections originating from the router's IP address
• Modified router configuration or firmware settings without administrator action

Detection Strategies

• Monitor network traffic for HTTP requests to DIR-605L management interfaces with abnormally large parameter values
• Implement intrusion detection rules to flag requests targeting the formSetWAN_Wizard534 endpoint with oversized payloads
• Deploy network segmentation to isolate legacy IoT devices from critical network resources
• Utilize SentinelOne Singularity to detect anomalous behavior patterns indicative of exploitation attempts

Monitoring Recommendations

• Enable logging on network firewalls to capture all traffic to and from DIR-605L devices
• Establish baseline behavior profiles for router management interface access patterns
• Configure alerts for any firmware modification attempts or unexpected configuration changes
• Regularly audit connected devices for signs of compromise or unusual activity

How to Mitigate CVE-2025-4441

Immediate Actions Required

• Replace the D-Link DIR-605L with a supported router model that receives security updates
• If immediate replacement is not possible, disable remote management access to the router
• Implement network segmentation to isolate the vulnerable device from sensitive network segments
• Restrict access to the router's web management interface to trusted IP addresses only

Patch Information

No security patch is available for this vulnerability. The D-Link DIR-605L has reached end-of-life status and is no longer supported by the vendor. D-Link was contacted about this disclosure but will not be releasing a fix as the product is discontinued. Organizations using this device should plan for immediate replacement with a currently supported router model.

For additional information, refer to the VulDB entry and the D-Link official website for supported product alternatives.

Workarounds

• Disable the WAN configuration wizard functionality if possible through router settings
• Implement strict firewall rules to block external access to the router's management interface (typically ports 80/443)
• Use a VPN or jump host architecture to access router management when remote administration is required
• Consider deploying a network-level firewall or IPS in front of the vulnerable device to filter malicious requests

# Example: Block external access to router management interface using iptables on upstream firewall
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 specific trusted IP
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT