BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`_CVE-2026-40279

3.7 / 10

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

Basic Information

ID CVE-2026-40279

Source GitHub_M

Published Apr 21, 2026 at 16:29

Affected Product

Vendor bacnet-stack

Product bacnet-stack

Version < 1.4.3

Affected Versions bacnet-stack bacnet-stack < 1.4.3

CWE Classification

CWE-758

References

github.com /bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv

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    "published": "2026-04-21T16:29:16.125Z",
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