An issue was discovered in OpenNDS Captive Portal before version 10.1.2. It has a NULL pointer dereference in preauthenticated() that can be triggered with a crafted GET HTTP request with a missing redirect query string parameter. Triggering this issue results in crashing OpenNDS (a Denial-of-Service condition). Affected OpenNDS Captive Portal before version 10.1.2 fixed infixed in OpenWrt master, OpenWrt 23.05 and OpenWrt 22.03 on28. August 2023 by updating OpenNDS to version 10.1.3.