Edimax EW-7438RPn Stack-Based Buffer Overflow Vulnerability (CVE-2026-9481)

A critical stack-based buffer overflow vulnerability, identified as CVE-2026-9481, has been discovered in Edimax EW-7438RPn version 1.31. This vulnerability resides within the formStats function located in the /goform/formStats file. The vulnerability stems from improper input validation of the submit-url argument, allowing a remote attacker to potentially overwrite parts of the stack. Publicly available exploit code exists, increasing the risk of widespread exploitation. The vendor was notified but did not respond, increasing the urgency for users to apply mitigations.

Attack Chain

1. The attacker sends a specially crafted HTTP request to the Edimax EW-7438RPn device.
2. The HTTP request targets the /goform/formStats endpoint.
3. The request includes the submit-url argument with a value exceeding the expected buffer size.
4. The formStats function processes the submit-url argument without proper bounds checking.
5. The excessive length of the submit-url argument causes a buffer overflow on the stack.
6. The attacker overwrites critical data on the stack, such as the return address.
7. Upon function return, control is redirected to an address specified by the attacker.
8. The attacker executes arbitrary code on the device, potentially gaining full control.

Impact

Successful exploitation of CVE-2026-9481 allows a remote attacker to execute arbitrary code on the vulnerable Edimax EW-7438RPn device. Given the device’s likely placement as a network gateway or access point, this could lead to complete compromise of the network, data exfiltration, or denial-of-service conditions. The number of affected devices is unknown, but the existence of public exploit code increases the likelihood of widespread attacks targeting this vulnerability.

Recommendation

• Deploy the Sigma rule “Detect CVE-2026-9481 Exploitation Attempt via Long submit-url” to identify potential exploitation attempts in web server logs.
• Monitor webserver logs for abnormal POST requests to the /goform/formStats endpoint, looking for unusually long submit-url parameters.
• Apply network intrusion detection rules that look for patterns indicative of buffer overflow attempts in HTTP requests targeting Edimax EW-7438RPn devices.