CVE-2025-60566: D-Link DIR-600L Buffer Overflow Flaw

CVE-2025-60566 Overview

CVE-2025-60566 is a stack-based buffer overflow vulnerability (CWE-121) affecting the D-Link DIR-600L wireless router. The vulnerability exists in the formSetMACFilter function within the device firmware, where improper validation of the curTime parameter allows an attacker to overflow a stack buffer. This firmware vulnerability in an embedded network device can be exploited remotely without authentication to cause a denial of service condition.

Critical Impact

Remote unauthenticated attackers can exploit this buffer overflow to crash the router, disrupting network connectivity for all connected devices.

Affected Products

• D-Link DIR-600L Firmware version 1.16WWb01
• D-Link DIR-600L Hardware revision A1
• D-Link DIR-600L Ax series routers running vulnerable firmware

Discovery Timeline

• 2025-10-24 - CVE-2025-60566 published to NVD
• 2025-10-28 - Last updated in NVD database

Technical Details for CVE-2025-60566

Vulnerability Analysis

This vulnerability is a classic stack-based buffer overflow (CWE-121) in embedded router firmware. The formSetMACFilter function processes user-supplied input through the curTime parameter without proper bounds checking. When a specially crafted request containing an oversized curTime value is submitted to the device, the function copies this data into a fixed-size stack buffer, overwriting adjacent memory regions including the return address.

The network-accessible attack vector means this vulnerability can be exploited remotely. No authentication is required to trigger the vulnerable code path, making this a particularly dangerous flaw in home and small office network environments. The impact is primarily focused on availability, as successful exploitation causes the device to crash or become unresponsive.

Root Cause

The root cause is a missing boundary check in the formSetMACFilter function when handling the curTime parameter. The firmware fails to validate the length of user input before copying it into a stack-allocated buffer, allowing attackers to write beyond the buffer boundaries. This is a common vulnerability pattern in embedded C/C++ code where developers use unsafe string handling functions without proper size validation.

Attack Vector

The vulnerability is exploitable over the network through the router's web management interface. An attacker can send a malicious HTTP request to the device containing an oversized curTime parameter value. The attack does not require any user interaction or prior authentication, making it trivially exploitable by anyone who can reach the router's management interface.

The exploitation flow involves:

1. Identifying a vulnerable D-Link DIR-600L device on the network
2. Crafting an HTTP request targeting the MAC filter configuration endpoint
3. Including an oversized curTime parameter designed to overflow the stack buffer
4. Sending the request to trigger the buffer overflow and crash the device

For detailed technical analysis and proof-of-concept information, see the GitHub PoC for DLINK DIR600LAx.

Detection Methods for CVE-2025-60566

Indicators of Compromise

• Unexpected router reboots or unresponsive behavior
• HTTP requests to the router's web interface containing abnormally long curTime parameter values
• Network logs showing repeated connection attempts to the router management interface from unknown sources
• Crash logs or core dumps on the device (if accessible) indicating stack corruption

Detection Strategies

• Monitor network traffic for HTTP requests to D-Link router management interfaces with unusually large parameter values
• Implement intrusion detection rules to flag requests containing oversized curTime values targeting formSetMACFilter endpoints
• Deploy network segmentation to isolate IoT devices and monitor traffic crossing segment boundaries
• Use SentinelOne Singularity to detect anomalous network behavior patterns associated with embedded device exploitation

Monitoring Recommendations

• Configure network monitoring to alert on unexpected router restarts or connectivity losses
• Enable logging on firewall devices to capture traffic destined for router management ports
• Implement real-time alerting for unusual patterns of access to network infrastructure devices
• Consider deploying network-level anomaly detection to identify exploitation attempts

How to Mitigate CVE-2025-60566

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required for operations
• Implement firewall rules to block external access to the router's administrative ports
• Consider replacing end-of-life D-Link DIR-600L devices with supported models

Patch Information

As of the last NVD update on 2025-10-28, no vendor patch has been released for this vulnerability. The D-Link DIR-600L is a legacy product that may no longer receive security updates. Organizations should check the D-Link support website for any firmware updates and consider device replacement if patches are not available.

Workarounds

• Disable the web-based management interface and use console access only if possible
• Implement network segmentation to isolate the vulnerable router from untrusted networks
• Configure upstream firewall rules to block malicious requests before they reach the device
• Replace the vulnerable device with a currently supported router model that receives security updates

# Example iptables rules to restrict router management access
# Block external access to router management port (adjust IP and port as needed)
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 suspicious access attempts
iptables -A INPUT -p tcp --dport 80 -j LOG --log-prefix "Router-Access: "