PT-2026-34009 · Bacnet Stack · Bacnet Stack

Published 2026-04-21 · Updated 2026-04-21 · CVE-2026-40279

Mitre

CVSS v3.1

3.7

Low

AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

Fix

Weakness Enumeration

CWE-758

Related Identifiers

CVE-2026-40279

Affected Products

Bacnet Stack

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-40279 · Security Note
• https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv · Note
• https://twitter.com/CVEnew/status/2046636244415754576 · Twitter Post