CVE-2026-9480 Overview
CVE-2026-9480 is a stack-based buffer overflow [CWE-119] in the Edimax EW-7438RPn wireless range extender running firmware version 1.31. The flaw resides in the formrefresh function handling requests to /goform/formrefresh. Attackers manipulate the submit-url argument to overflow a fixed-size stack buffer. The vulnerability is exploitable remotely over the network and requires low-level privileges. A public exploit exists, increasing the risk of opportunistic attacks against exposed devices. The vendor was contacted prior to disclosure but did not respond, leaving affected devices without an official patch.
Critical Impact
Remote attackers with low privileges can corrupt stack memory on Edimax EW-7438RPn 1.31 devices through the submit-url parameter, potentially leading to arbitrary code execution or device compromise.
Affected Products
- Edimax EW-7438RPn firmware version 1.31
- formrefresh handler in /goform/formrefresh
- submit-url parameter processing routine
Discovery Timeline
- 2026-05-25 - CVE-2026-9480 published to NVD
- 2026-05-26 - Last updated in NVD database
Technical Details for CVE-2026-9480
Vulnerability Analysis
The vulnerability is a classic stack-based buffer overflow [CWE-119] in the embedded web management interface of the Edimax EW-7438RPn range extender. The formrefresh function processes the submit-url HTTP parameter without enforcing length checks before copying it into a fixed-size stack buffer. An attacker submits an oversized value to /goform/formrefresh and overwrites adjacent stack memory, including saved return addresses.
The affected device runs a Linux-based firmware on a MIPS or ARM architecture typical of consumer wireless extenders. Successful overflow allows control over execution flow. The public availability of the exploit lowers the barrier for attackers targeting exposed administrative interfaces.
Root Cause
The formrefresh handler uses an unsafe string copy operation against the submit-url argument. The function lacks bounds validation, allowing user-supplied data to exceed the destination buffer on the stack. This pattern reflects a common firmware coding flaw where input length is trusted without verification.
Attack Vector
The attack vector is network-based. An attacker reaches the device's HTTP management interface and submits a crafted POST or GET request to /goform/formrefresh containing an oversized submit-url parameter. Low privileges are required, meaning the attacker must hold valid credentials or reach an interface that accepts unauthenticated submissions to the form handler. The exploit is publicly available, as referenced in the GitHub Vulnerability Details and VulDB #365461 records.
No verified code examples are available. See the GitHub Vulnerability Details for technical reproduction steps.
Detection Methods for CVE-2026-9480
Indicators of Compromise
- HTTP requests to /goform/formrefresh containing abnormally long submit-url parameter values
- Unexpected reboots or crashes of the Edimax EW-7438RPn web service following inbound HTTP traffic
- Outbound connections from the device to unfamiliar hosts after suspicious management-plane activity
Detection Strategies
- Inspect HTTP request bodies and query strings targeting /goform/formrefresh for submit-url values exceeding typical URL length thresholds
- Deploy network intrusion detection signatures matching long submit-url payloads against the management interface
- Correlate device crash logs with preceding HTTP traffic to identify exploitation attempts
Monitoring Recommendations
- Restrict and log all access to the device's management interface from non-administrative network segments
- Alert on repeated POST requests to /goform/formrefresh from a single source within a short interval
- Track firmware version inventory to identify exposed Edimax EW-7438RPn 1.31 devices
How to Mitigate CVE-2026-9480
Immediate Actions Required
- Remove the Edimax EW-7438RPn 1.31 management interface from any internet-facing or untrusted network
- Place affected devices on an isolated VLAN restricted to authorized administrative hosts
- Rotate administrative credentials on the device to limit access to the vulnerable handler
- Plan replacement of the device since the vendor has not responded to disclosure
Patch Information
No vendor patch is available. The vendor did not respond to disclosure attempts according to the VulDB #365461 record. Organizations should treat affected hardware as end-of-support and prioritize replacement with a maintained product.
Workarounds
- Disable remote management on the WAN interface and limit administration to wired LAN access
- Block inbound traffic to the device's HTTP management port at the upstream firewall
- Apply network ACLs that permit access to /goform/formrefresh only from a dedicated management workstation
- Monitor for and decommission Edimax EW-7438RPn 1.31 devices that cannot be isolated
# Example firewall rule to restrict access to the device management interface
# Replace 192.0.2.10 with the device IP and 10.0.0.5 with the admin workstation
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -s 10.0.0.5 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
