BACnet Stack CVE-2026-40279

| EUVD-2026-24166 LOW
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior (CWE-758)
2026-04-21 GitHub_M
Buffer Overflow
3.7
CVSS 3.1

CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

2
Patch available
Apr 21, 2026 - 18:01 EUVD
Analysis Generated
Apr 21, 2026 - 17:38 vuln.today

DescriptionNVD

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.

AnalysisAI

BACnet Stack prior to version 1.4.3 exhibits undefined behavior in the decode_signed32() function when processing signed-integer property values containing bytes with the high bit set, causing denial of service through integer overflow. Network-remote attackers can trigger this vulnerability by sending specially crafted BACnet packets with high-bit-set byte sequences, resulting in application instability or crash on embedded systems running vulnerable versions. …

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CVE-2026-40279 vulnerability details – vuln.today
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