CVE-2026-40279

LOW

3.7

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.

CVE Details

CVSS v3.1 Score3.7

SeverityLOW

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

Attack VectorNETWORK

ComplexityHIGH

Privileges RequiredNONE

User InteractionNONE

Published4/21/2026

Last Modified4/22/2026

Sourcenvd

Honeypot Sightings0

Weaknesses (CWE)

CWE-758

References

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv(security-advisories@github.com)

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv(134c704f-9b21-4f2e-91b3-4a467353bcc0)

IOC Correlations

No correlations recorded

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