Edimax EW-7438RPn Stack-Based Buffer Overflow Vulnerability (CVE-2026-9463)

CVE-2026-9463 describes a stack-based buffer overflow vulnerability affecting Edimax EW-7438RPn version 1.31. The vulnerability resides in the formLicence function within the /goform/formLicence file. A remote attacker can trigger this vulnerability by manipulating the submit-url argument, potentially leading to arbitrary code execution. The vendor has been notified but has not responded. Publicly available exploit code exists, increasing the risk of exploitation. This vulnerability matters to defenders because it allows unauthenticated attackers to compromise the device remotely, potentially gaining control of the network it serves.

Attack Chain

1. The attacker sends a crafted HTTP request to the /goform/formLicence endpoint of the Edimax EW-7438RPn device.
2. The request includes a malicious submit-url argument containing a string longer than the allocated buffer size within the formLicence function.
3. The device processes the HTTP request and calls the formLicence function with the attacker-controlled submit-url argument.
4. Due to insufficient bounds checking, the oversized submit-url argument overwrites the stack buffer.
5. The attacker precisely crafts the overflow to overwrite critical data on the stack, such as the return address.
6. The formLicence function completes its execution and attempts to return.
7. Instead of returning to the legitimate caller, the overwritten return address redirects execution to attacker-controlled code.
8. The attacker gains arbitrary code execution on the device, potentially leading to full system compromise.

Impact

Successful exploitation of CVE-2026-9463 allows a remote attacker to execute arbitrary code on the Edimax EW-7438RPn device. Given the nature of buffer overflows, this can result in complete system compromise, allowing the attacker to control the device, potentially pivot to other devices on the network, and intercept or manipulate network traffic. The vulnerability affects Edimax EW-7438RPn version 1.31. The number of affected devices is unknown, but exploitation could lead to widespread disruption of home and small business networks.

Recommendation

• Deploy the Sigma rule Detect CVE-2026-9463 Exploitation Attempt to detect malicious HTTP requests targeting the vulnerable endpoint and argument.
• Monitor web server logs for suspicious requests to /goform/formLicence containing unusually long submit-url parameters to identify potential exploitation attempts.
• Since no patch is available, consider replacing the affected Edimax EW-7438RPn device with a more secure alternative.