CVE-2025-4141: Netgear EX6200 Buffer Overflow Vulnerability

CVE-2025-4141 Overview

A critical buffer overflow vulnerability has been identified in the Netgear EX6200 WiFi range extender running firmware version 1.0.3.94. The vulnerability exists within the function sub_3C03C, where improper handling of the host argument allows an attacker to trigger a buffer overflow condition. This vulnerability can be exploited remotely over the network by an authenticated attacker, potentially leading to arbitrary code execution, device compromise, or denial of service.

The vendor, Netgear, was contacted early about this disclosure but did not respond in any way, leaving affected devices without an official patch.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially execute arbitrary code on the affected Netgear EX6200 device, compromising network security and enabling lateral movement within the network.

Affected Products

• Netgear EX6200 WiFi Range Extender
• Netgear EX6200 Firmware version 1.0.3.94

Discovery Timeline

• 2025-04-30 - CVE-2025-4141 published to NVD
• 2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4141

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 flaw resides in the sub_3C03C function of the Netgear EX6200 firmware, which processes the host argument without proper bounds checking.

When a maliciously crafted input is provided to the host parameter, the function fails to validate the length of the input data before copying it into a fixed-size buffer. This allows an attacker to write data beyond the allocated buffer boundaries, potentially overwriting adjacent memory regions including return addresses, function pointers, or other critical program data.

The vulnerability is remotely exploitable over the network and requires only low-level privileges to execute, making it particularly dangerous for devices exposed to untrusted networks.

Root Cause

The root cause of this vulnerability is insufficient input validation and improper bounds checking in the sub_3C03C function. The function accepts a host argument and copies it into a fixed-size memory buffer without verifying that the input length does not exceed the buffer capacity. This classic buffer overflow pattern allows attackers to write arbitrary data past the buffer boundary, corrupting adjacent memory structures.

Attack Vector

The attack can be initiated remotely over the network by an authenticated user. An attacker would craft a specially malformed request containing an oversized host parameter value, which when processed by the vulnerable function, triggers the buffer overflow condition.

The attack flow typically involves:

1. Establishing a connection to the target Netgear EX6200 device
2. Authenticating with valid credentials (low privilege level sufficient)
3. Sending a crafted request with an oversized host parameter
4. The overflow overwrites critical memory structures
5. Potential code execution or device crash occurs

Technical details and proof-of-concept information are available in the GitHub Buffer Overflow PoC repository.

Detection Methods for CVE-2025-4141

Indicators of Compromise

• Unexpected device reboots or crashes of the Netgear EX6200 range extender
• Unusual network traffic patterns originating from or directed to the device management interface
• Anomalous memory consumption or process behavior on the affected device
• Authentication attempts followed by malformed HTTP requests with oversized parameters

Detection Strategies

• Monitor network traffic for abnormally large HTTP request parameters targeting Netgear device management interfaces
• Implement network intrusion detection rules to identify buffer overflow exploitation patterns against embedded devices
• Deploy network segmentation to isolate IoT and network infrastructure devices from untrusted networks
• Enable logging on network firewalls to capture suspicious traffic to device management ports

Monitoring Recommendations

• Continuously monitor firmware versions across all Netgear devices in your environment
• Implement network anomaly detection for traffic to and from WiFi extenders and similar IoT devices
• Establish baseline behavior for device management traffic and alert on deviations
• Consider deploying SentinelOne Singularity for comprehensive network visibility and threat detection

How to Mitigate CVE-2025-4141

Immediate Actions Required

• Restrict network access to the Netgear EX6200 management interface to trusted IP addresses only
• Disable remote management features if not required
• Implement strong, unique authentication credentials on all affected devices
• Consider replacing affected devices with supported models that receive regular security updates
• Isolate affected devices on a separate network segment

Patch Information

No official patch is currently available from Netgear. The vendor was contacted early about this disclosure but did not respond. Users should monitor the Netgear Official Website for any future security advisories or firmware updates.

Given the lack of vendor response, organizations should prioritize alternative mitigation strategies and consider device replacement with actively supported networking equipment.

Workarounds

• Implement firewall rules to block external access to the device management interface (typically ports 80/443)
• Configure access control lists (ACLs) to restrict management access to specific trusted IP addresses
• Disable any unnecessary services on the device to reduce the attack surface
• Place the device behind a network firewall or UTM that can inspect and filter malicious traffic

# Example firewall rule to restrict management access (iptables)
# Block external access to the EX6200 management interface
iptables -A FORWARD -d <EX6200_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <EX6200_IP> -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin workstation
iptables -I FORWARD -s <ADMIN_IP> -d <EX6200_IP> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s <ADMIN_IP> -d <EX6200_IP> -p tcp --dport 443 -j ACCEPT