CVE-2026-40279 BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, decodesigned32 in src/bacnet/bacint.c reconstructs a 32-bit signed integer from four APDU bytes using signed left shifts. When any of the four bytes has bit 7 set value ≥ 0x80, the left-shift...

CVE-2026-40279

BACnet Stack (open-source C library for embedded systems) contains a defect in decode_signed32() in src/bacnet/bacint.c where reconstructing a 32-bit signed integer from four APDU bytes via signed left shifts can overflow signed int32_t when any byte has bit 7 set (>= 0x80). This undefined beh...