medium5.5
CVE-2026-21870
BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services.
Impact
BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Bacnetstack | Bacnet Stack | through 1.4.2 Version 1.5.0 |