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.

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History

Wed, 22 Apr 2026 00:00:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 21 Apr 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Bacnetstack
Bacnetstack bacnet Stack
Vendors & Products Bacnetstack
Bacnetstack bacnet Stack

Tue, 21 Apr 2026 16:45:00 +0000

Type Values Removed Values Added
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.
Title BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`
Weaknesses CWE-758
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-21T19:18:58.492Z

Reserved: 2026-04-10T20:22:44.034Z

Link: CVE-2026-40279

cve-icon Vulnrichment

Updated: 2026-04-21T19:03:16.067Z

cve-icon NVD

Status : Received

Published: 2026-04-21T17:16:54.853

Modified: 2026-04-21T20:16:59.027

Link: CVE-2026-40279

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-21T17:30:37Z

Weaknesses