CVE-2026-9424: Edimax EW-7438RPn RCE Vulnerability

CVE-2026-9424 Overview

CVE-2026-9424 is an operating system command injection vulnerability in the Edimax EW-7438RPn Wi-Fi range extender, firmware version 1.31. The flaw resides in the formWlanMP function within /goform/formWlanMP, part of the Content-Type handler. Attackers can manipulate numerous request arguments, including ateFunc, ateGain, ateTxCount, ateChan, ateRate, ateMacID, and multiple e2pTxPower parameters, to inject shell commands. Exploitation is remote and a public proof-of-concept exists. The vendor was contacted prior to disclosure but did not respond. The weakness is tracked under CWE-77.

Critical Impact

Authenticated remote attackers can inject arbitrary operating system commands on affected Edimax EW-7438RPn devices through the formWlanMP handler, with a public exploit already available.

Affected Products

• Edimax EW-7438RPn firmware version 1.31
• /goform/formWlanMP Content-Type handler component
• Devices exposing the administrative web interface over the network

Discovery Timeline

• 2026-05-25 - CVE-2026-9424 published to NVD
• 2026-05-26 - Last updated in NVD database

Technical Details for CVE-2026-9424

Vulnerability Analysis

The vulnerability exists in the formWlanMP function, which processes wireless test-mode and EEPROM configuration parameters submitted through the device web interface at /goform/formWlanMP. The handler accepts more than two dozen attacker-controlled arguments, including ateFunc, ateGain, ateTxCount, ateChan, ateRate, ateMacID, e2pTxPower1 through e2pTxPower7, e2pTx2Power1 through e2pTx2Power7, ateTxFreqOffset, ateMode, ateBW, ateAntenna, e2pTxFreqOffset, e2pTxPwDeltaB, e2pTxPwDeltaG, e2pTxPwDeltaMix, e2pTxPwDeltaN, and readE2P. These values are passed into operating system command invocations without proper sanitization.

Because the parameters are concatenated into shell commands, attackers can append shell metacharacters such as ;, |, or backticks to execute arbitrary commands in the device firmware context. EPSS scoring places the likelihood of exploitation in the 77th percentile, reflecting that working exploit code is already public.

Root Cause

The root cause is improper neutralization of special elements used in an operating system command [CWE-77]. The formWlanMP handler treats user-supplied form fields as trusted input and forwards them into system shell calls. No allowlist, escaping, or argument separation prevents shell interpretation of injected characters.

Attack Vector

An attacker reaches the vulnerable endpoint over the network by submitting a crafted POST request to /goform/formWlanMP with manipulated values in any of the listed parameters. The attack requires low privileges on the web interface and no user interaction. Successful exploitation yields command execution within the embedded Linux environment of the range extender, enabling persistence, credential theft, and lateral pivoting into the local wireless network.

The vulnerability is described in detail in the public proof-of-concept hosted in the GitHub vulnerability documentation.

Detection Methods for CVE-2026-9424

Indicators of Compromise

• HTTP POST requests to /goform/formWlanMP containing shell metacharacters such as ;, |, &, or backticks in any ate* or e2p* parameter.
• Outbound connections from the Edimax EW-7438RPn to unexpected hosts following web administrative activity.
• Unusual processes spawned from the embedded web server, such as telnetd, wget, or sh invoked with attacker-controlled arguments.

Detection Strategies

• Inspect web server and reverse-proxy logs in front of the device for requests to /goform/formWlanMP originating from unexpected source addresses.
• Deploy network intrusion detection signatures that flag shell metacharacters in POST bodies targeting the formWlanMP endpoint.
• Compare device configuration and firmware integrity against a known-good baseline to identify tampering.

Monitoring Recommendations

• Monitor network segments containing the Edimax EW-7438RPn for anomalous DNS resolution and outbound TCP connections to non-corporate destinations.
• Alert on administrative authentication events to the device followed by abnormal request volumes to /goform/ endpoints.
• Centralize syslog from network appliances and correlate with endpoint telemetry to identify lateral movement attempts.

How to Mitigate CVE-2026-9424

Immediate Actions Required

• Restrict management access to the Edimax EW-7438RPn web interface to trusted administrative VLANs only.
• Change default credentials and enforce strong authentication for the device web console.
• Place affected devices behind a network access control list that blocks untrusted sources from reaching /goform/formWlanMP.
• Decommission or replace the device if it is exposed to the internet or to untrusted user networks.

Patch Information

No vendor patch is available. The vendor was contacted in advance of disclosure but did not respond, as recorded in the VulDB #365405 advisory. Organizations should treat the device as unpatched and apply compensating controls until Edimax issues fixed firmware or the device is retired.

Workarounds

• Disable remote administration and ensure the web interface is only reachable from a dedicated management network.
• Segment the range extender from corporate endpoints and servers using firewall rules to contain post-exploitation activity.
• Replace the EW-7438RPn with a currently supported access point or range extender that receives security updates.

# Example firewall rule to restrict access to the device web interface
# Replace 192.0.2.10 with the device IP and 10.0.100.0/24 with the management subnet
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -s 10.0.100.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 443 -j DROP