CVE-2026-40279
Description
BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, decode_signed32() 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 operation overflows a signed int32_t, which is undefined behavior per the C standard. This is flagged thousands of times per minute by UndefinedBehaviorSanitizer on any BACnet input containing signed-integer property values with high-bit-set bytes. This vulnerability is fixed in 1.4.3.
How to fix
- bacnetstack bacnet_stack1.4.3 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| bacnetstack bacnet_stack | v < 1.4.3 | 1.4.3 |
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