D-Link DIR-823X NULL Pointer Dereference Vulnerability in Wi-Fi Blacklist Management

A null pointer dereference vulnerability has been identified in the D-Link DIR-823X router, specifically in the 240126 and 240802 firmware versions. The issue arises in the 'set_wifi_blacklists' function within the '/goform/set_wifi_blacklists' file, part of the HTTP POST request handler. The vulnerability is triggered by manipulating the 'macList' parameter, leading to a crash as the application attempts to dereference a null pointer. This vulnerability can be exploited remotely, and a public proof-of-concept exploit is available.

Impact

Exploitation of this vulnerability causes the router to crash, disrupting its normal operation and availability.

Reproduction

To reproduce this vulnerability, send a POST request to the '/goform/set_wifi_blacklists' endpoint with a crafted 'macList' parameter that includes malicious input, such as 'jX%n'. This input bypasses the application's validation, causing a null pointer dereference when the server processes the request.

Remediation

It is recommended to apply restrictive firewall rules to block or limit access to the vulnerable router.