CVE-2025-4122: Netgear JWNR2000v2 Firmware RCE Vulnerability

CVE-2025-4122 Overview

CVE-2025-4122 is a command injection vulnerability in the Netgear JWNR2000v2 wireless router running firmware version 1.0.0.11. The flaw resides in the sub_435E04 function, where the host argument is passed to a system command without proper sanitization. Authenticated remote attackers can manipulate this parameter to execute arbitrary operating system commands on the router. The vendor was contacted before public disclosure but did not respond. The weakness is tracked under [CWE-74] (Improper Neutralization of Special Elements) and [CWE-77] (Command Injection).

Critical Impact
Successful exploitation grants attackers the ability to run arbitrary shell commands on the router, enabling persistent network compromise, traffic interception, and lateral movement into connected networks.

Affected Products

Netgear JWNR2000v2 router (hardware)
Netgear JWNR2000v2 firmware version 1.0.0.11
Deployments exposing the router web management interface to untrusted networks

Discovery Timeline

2025-04-30 - CVE-2025-4122 published to the National Vulnerability Database
2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4122

Vulnerability Analysis

The vulnerability exists in the sub_435E04 function within the JWNR2000v2 firmware binary. This function processes the host parameter supplied through the device's web interface during authenticated MAC-related operations. The function constructs a shell command string that incorporates the attacker-controlled host value without escaping or filtering shell metacharacters.

When the resulting string is passed to a command execution primitive such as system(), injected characters like ;, |, or backticks break out of the intended command context. The router then executes attacker-supplied commands with the privileges of the web service, which typically runs as root on embedded Netgear devices. Refer to the GitHub README on Command Injection for the reverse-engineering details published by the researcher.

Root Cause

The root cause is missing input validation on the host parameter inside sub_435E04. The firmware concatenates user input directly into a shell command instead of using parameterized execution or strict allowlists. Embedded HTTP handlers in older Netgear consumer routers commonly invoke system() style functions with untrusted strings, and JWNR2000v2 follows this pattern.

Attack Vector

The attack vector is network-based and requires low-privilege authentication to the router's web interface. An attacker who has captured or guessed valid credentials sends a crafted HTTP request containing shell metacharacters in the host field. The malicious payload reaches sub_435E04, which executes the injected commands as the underlying web daemon user. Because the JWNR2000v2 is end-of-life and unlikely to receive vendor patches, exposed devices remain persistently vulnerable.

No public exploit code or proof-of-concept binary has been released beyond the technical write-up referenced in VulDB Entry #306602.

Detection Methods for CVE-2025-4122

Indicators of Compromise

HTTP POST or GET requests to the router's management interface containing shell metacharacters such as ;, |, &, or backticks in the host parameter
Unexpected outbound connections from the router to attacker-controlled infrastructure following authenticated administrative sessions
New or modified scripts in writable firmware paths such as /tmp or /var on the device
Unauthorized DNS configuration changes redirecting client traffic through external resolvers

Detection Strategies

Inspect web server logs on the router, where available, for parameter values that include shell metacharacters in MAC or host fields
Deploy network intrusion detection signatures that flag HTTP requests targeting Netgear administrative endpoints with command injection patterns
Monitor for anomalous traffic volumes or protocols originating from the router's LAN or WAN interface

Monitoring Recommendations

Forward router syslog output to a centralized logging platform and alert on administrative authentication followed by unusual command-line activity
Baseline normal router-originated traffic and alert on deviations such as outbound SSH, IRC, or unknown TCP ports
Track DNS resolver settings and firmware integrity through periodic configuration audits

How to Mitigate CVE-2025-4122

Immediate Actions Required

Disable remote (WAN-side) administration on the JWNR2000v2 immediately and restrict the web interface to trusted management hosts on the LAN
Rotate all administrative credentials and enforce strong, unique passwords to reduce the risk of credential-based exploitation
Plan replacement of the JWNR2000v2 with a currently supported router model, as this device is end-of-life

Patch Information

No vendor patch is available. Netgear did not respond to the researcher's disclosure attempts referenced in VulDB CTI Entry #306602. The JWNR2000v2 product line is end-of-life and is unlikely to receive a firmware fix. Organizations should treat replacement as the only durable remediation. Refer to the Netgear Official Website for current supported product lines.

Workarounds

Place the router behind an upstream firewall and block inbound access to TCP ports 80 and 443 on the device from untrusted networks
Segment the router onto an isolated management VLAN so that compromise cannot pivot directly into production assets
Disable any optional services such as UPnP, remote management, and cloud connectivity that increase the device's attack surface
Audit connected clients and revoke access for unknown devices to limit the pool of potential authenticated attackers

bash

# Configuration example: block external access to the router admin interface
# Run on an upstream firewall (example using iptables)
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -i <wan_iface> -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -i <wan_iface> -j DROP