CVE-2026-40279

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.

CVSS v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv	Exploit Mitigation Vendor Advisory
https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv	Exploit Mitigation Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-21 17:16

Updated : 2026-06-17 10:44

NVD link : CVE-2026-40279

Mitre link : CVE-2026-40279

CVE.ORG link : CVE-2026-40279

JSON object : View

Products Affected

bacnetstack

bacnet_stack

CWE

CWE-758

Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

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