CVE-2025-4142: Netgear EX6200 Buffer Overflow Vulnerability

CVE-2025-4142 Overview

A critical buffer overflow vulnerability has been discovered in Netgear EX6200 firmware version 1.0.3.94. This vulnerability affects the function sub_3C8EC, where improper handling of the host argument leads to a classic buffer overflow condition. The attack can be initiated remotely over the network, allowing attackers to potentially execute arbitrary code or cause denial of service on affected devices.

The vendor was contacted early about this disclosure but did not respond in any way, leaving users of affected devices without an official patch at the time of publication.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially gain full control of affected Netgear WiFi range extenders, compromising network security and enabling further attacks on connected devices.

Affected Products

• Netgear EX6200 Firmware version 1.0.3.94
• Netgear EX6120 (potentially affected)

Discovery Timeline

• April 30, 2025 - CVE-2025-4142 published to NVD
• May 12, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4142

Vulnerability Analysis

This buffer overflow vulnerability resides in the sub_3C8EC function of the Netgear EX6200 firmware. The function fails to properly validate the length of user-supplied input through the host argument before copying it into a fixed-size buffer. This classic memory corruption pattern allows attackers to write data beyond the allocated buffer boundaries, potentially overwriting adjacent memory regions including return addresses and function pointers.

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), which are among the most dangerous software weaknesses due to their potential for arbitrary code execution.

Root Cause

The root cause of this vulnerability is the absence of proper bounds checking in the sub_3C8EC function when processing the host parameter. The firmware code copies user-controlled data into a stack or heap buffer without verifying that the input length does not exceed the destination buffer's capacity. This lack of input validation is a common vulnerability pattern in embedded device firmware, where resource constraints sometimes lead developers to omit security checks.

Attack Vector

The vulnerability is exploitable remotely over the network. An authenticated attacker with low privileges can send a specially crafted request containing an oversized host value to trigger the buffer overflow. The attack does not require user interaction and can be executed directly against the device's web management interface or related network services.

The exploitation mechanism involves:

1. Identifying a Netgear EX6200 device running vulnerable firmware version 1.0.3.94
2. Crafting a malicious request with an oversized host parameter
3. Sending the request to trigger the sub_3C8EC function
4. Overflowing the buffer to overwrite critical memory structures
5. Gaining code execution or causing denial of service

For detailed technical analysis and proof-of-concept information, refer to the GitHub PoC Repository and VulDB #306634.

Detection Methods for CVE-2025-4142

Indicators of Compromise

• Unusual network traffic patterns targeting the Netgear device management interface
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Suspicious HTTP requests with abnormally long host parameter values
• Device configuration changes not initiated by administrators
• Evidence of unauthorized access to the network through the compromised range extender

Detection Strategies

• Monitor network traffic for HTTP requests containing oversized parameters targeting Netgear devices
• Implement intrusion detection rules to alert on buffer overflow attack patterns
• Deploy network segmentation to isolate IoT and networking devices from critical infrastructure
• Enable logging on network firewalls to capture attempts to access device management interfaces
• Use vulnerability scanning tools to identify affected firmware versions in your environment

Monitoring Recommendations

• Regularly audit firmware versions across all Netgear devices in the network
• Configure SIEM rules to correlate multiple failed authentication attempts with suspicious requests
• Monitor for unexpected outbound connections from network infrastructure devices
• Establish baseline behavior for network devices to detect anomalous activity
• Implement network traffic analysis to identify potential exploitation attempts

How to Mitigate CVE-2025-4142

Immediate Actions Required

• Restrict access to the device management interface to trusted internal networks only
• Implement network segmentation to isolate affected devices from critical systems
• Consider replacing affected devices with supported models if no patch is available
• Monitor affected devices closely for signs of compromise
• Disable remote management features if not required

Patch Information

As of the last update on May 12, 2025, Netgear has not released a security patch for this vulnerability. The vendor was contacted early about this disclosure but did not respond. Users are advised to check the Netgear Official Website regularly for firmware updates and security advisories. Given the lack of vendor response, affected organizations should prioritize implementing workarounds and consider device replacement for critical environments.

Workarounds

• Restrict management interface access using firewall rules to allow only trusted IP addresses
• Place affected devices on isolated network segments with strict access controls
• Disable WAN-side management access to prevent remote exploitation
• Implement strong authentication and change default credentials
• Consider deploying a network-based Web Application Firewall (WAF) to filter malicious requests

# Example firewall rule to restrict access to device management interface
# Allow only trusted admin subnet to access the device
iptables -A FORWARD -d <DEVICE_IP> -p tcp --dport 80 -s <TRUSTED_SUBNET> -j ACCEPT
iptables -A FORWARD -d <DEVICE_IP> -p tcp --dport 443 -s <TRUSTED_SUBNET> -j ACCEPT
iptables -A FORWARD -d <DEVICE_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <DEVICE_IP> -p tcp --dport 443 -j DROP