CVE-2025-4147: Netgear EX6200 Buffer Overflow Vulnerability

CVE-2025-4147 Overview

CVE-2025-4147 is a buffer overflow vulnerability in the Netgear EX6200 WiFi range extender running firmware version 1.0.3.94. The flaw resides in the function sub_47F7C, where manipulation of the host argument triggers a buffer overflow condition. The vulnerability is remotely exploitable and requires low privileges with no user interaction. Netgear was contacted about this disclosure but did not respond, leaving affected devices without an official patch.

Critical Impact
Remote attackers with low-privileged access can trigger a buffer overflow in the sub_47F7C function of Netgear EX6200, potentially leading to arbitrary code execution and full compromise of confidentiality, integrity, and availability on the device.

Affected Products

Netgear EX6200 WiFi Range Extender (hardware)
Netgear EX6200 Firmware version 1.0.3.94
Deployments exposing the device management interface to untrusted networks

Discovery Timeline

2025-05-01 - CVE-2025-4147 published to the National Vulnerability Database (NVD)
2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4147

Vulnerability Analysis

The vulnerability is a classic buffer overflow [CWE-119, CWE-120] within the sub_47F7C function of the Netgear EX6200 firmware. The function processes the host argument without proper bounds checking before copying it into a fixed-size buffer. An attacker who supplies an oversized value for host can overwrite adjacent memory, including control flow structures on the stack or heap.

Successful exploitation can corrupt memory, crash the device, or allow attacker-controlled code to execute in the context of the vulnerable process. Because the EX6200 firmware runs on an embedded Linux platform with limited exploit mitigations, memory corruption frequently results in code execution rather than a simple denial-of-service.

Root Cause

The root cause is improper restriction of operations within the bounds of a memory buffer. The sub_47F7C function trusts the length of the host parameter supplied through the request without enforcing maximum input size or performing safe string copy operations. This is a recurring pattern in embedded HTTP/CGI handlers that use unsafe C functions such as strcpy or sprintf.

Attack Vector

The attack vector is the network. An attacker who can reach the EX6200 management service can send a crafted request containing an oversized host parameter to trigger the overflow. Exploitation requires low privileges, suggesting an authenticated session against the device. Devices exposed to the internet or shared networks face the highest exposure. Public technical details and proof-of-concept research are referenced in the GitHub Exploit Research repository and tracked under VulDB #306679.

No verified proof-of-concept code is reproduced here. See the GitHub research referenced above for technical details on the overflow trigger.

Detection Methods for CVE-2025-4147

Indicators of Compromise

Unexpected reboots, watchdog resets, or service crashes on the EX6200 device
Anomalous HTTP requests to the device administration interface containing unusually long host header values or host parameters
Outbound connections from the extender to unknown infrastructure, indicating possible post-exploitation activity
Configuration changes or new administrative sessions that do not correlate with legitimate admin activity

Detection Strategies

Inspect HTTP traffic destined for the EX6200 management interface for oversized parameter values, particularly in host fields
Correlate device crashes and restarts with preceding network traffic to identify exploitation attempts
Deploy network intrusion detection signatures targeting buffer overflow patterns against Netgear management endpoints
Baseline normal management traffic to the extender and alert on deviations in request size or frequency

Monitoring Recommendations

Capture and retain syslog and management-plane logs from the EX6200 in a centralized logging platform
Monitor DHCP and ARP tables for unauthorized devices communicating with the extender's admin interface
Track firmware version inventory across all Netgear devices to identify systems running vulnerable 1.0.3.94 firmware
Alert on any administrative authentication events from non-management network segments

How to Mitigate CVE-2025-4147

Immediate Actions Required

Restrict access to the EX6200 management interface to trusted management VLANs or specific administrator workstations
Disable remote management features and ensure the admin interface is not reachable from the WAN or guest networks
Rotate administrative credentials on all EX6200 devices and enforce strong, unique passwords
Evaluate whether the EX6200 can be replaced with a supported model, given the absence of a vendor response

Patch Information

No official patch is available at this time. According to the disclosure, the vendor was contacted but did not respond. Organizations should monitor the Netgear Official Website and VulDB #306679 - CTI for any future advisories or firmware updates addressing this issue.

Workarounds

Segment the EX6200 onto an isolated network with strict ACLs limiting which hosts can reach TCP management ports
Place the device behind a firewall that blocks inbound connections to its administration service from untrusted networks
Disable any unused services on the extender to reduce the attack surface
Consider decommissioning the device until a vendor patch is released, particularly in high-security environments

bash

# Example firewall rule to restrict management access to the EX6200
# Replace <MGMT_SUBNET> and <EX6200_IP> with environment-specific values
iptables -A FORWARD -s <MGMT_SUBNET> -d <EX6200_IP> -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d <EX6200_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <EX6200_IP> -p tcp --dport 443 -j DROP