Attack Chain

1. The attacker identifies an Edimax BR-6428nC device running a vulnerable firmware version (<= 1.16).
2. The attacker crafts a malicious HTTP POST request targeting the /goform/setWAN endpoint.
3. The request includes the pptpDfGateway parameter with a value exceeding the expected buffer size.
4. The device processes the request, and the oversized pptpDfGateway value overflows the buffer, overwriting adjacent memory regions.
5. The attacker carefully crafts the overflow to overwrite the return address, redirecting execution flow.
6. Execution is redirected to attacker-controlled code injected within the overflowed buffer.
7. The attacker gains arbitrary code execution on the device, potentially achieving full system control.
8. The attacker could then use this control to modify device settings, intercept network traffic, or establish a persistent backdoor.

Impact

Successful exploitation of this vulnerability can allow an attacker to gain complete control of the Edimax BR-6428nC device. This could enable the attacker to intercept and modify network traffic, access sensitive information, or use the device as a point of entry for further attacks within the network. Given the public availability of exploit code, the risk of widespread exploitation is significant.

Recommendation

• Deploy the Sigma rule Edimax_BR_6428nC_Buffer_Overflow_setWAN to detect suspicious HTTP requests targeting the vulnerable endpoint and parameter.
• Consider blocking or rate-limiting access to the /goform/setWAN endpoint from untrusted networks.
• Since the vendor is unresponsive and a patch is unlikely, network segmentation and access control policies are the best mitigation options.