BACnet Stack: Out-of-Bounds Read in WritePropertyMultiple Decoder via Deprecated Tag Parser

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an out-of-bounds read vulnerability in bacnet-stack's WritePropertyMultiple service decoder allows unauthenticated remote attackers to read past allocated buffer boundaries by sending a truncated WPM request. The vulnerability stems from wpm_decode_object_property() calling the deprecated decode_tag_number_and_value() function, which performs no bounds checking on the input buffer. A crafted BACnet/IP packet with a truncated property payload causes the decoder to read 1-7 bytes past the end of the buffer, leading to crashes or information disclosure on embedded BACnet devices. This vulnerability is fixed in 1.4.3.