CVE-2025-66624

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. Prior to 1.5.0.rc2, The npduisexpectedreply function in src/bacnet/npdu.c indexes requestpdu[offset+2/3/5] and replypdu[offset+1/2/4] without verifying that those APDU bytes exist. bacnetnpdu_decode() can return offset == 2 for a 2-byte NPDU, so tiny PDUs pass the version check and then get read out of bounds. On ASan/MPU/strict builds this is an immediate crash (DoS). On unprotected builds it is undefined behavior and can mis-route replies; RCE is unlikely because only reads occur, but DoS is reliable.