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CVE-2026-40279

3.7 · LOW

BACnet Stack is a BACnet open source protocol stack C library for embedded systems.

Published Apr 21, 2026CWE-758EPSS 0.33%

Overview

CVE-2026-40279 is a low-severity vulnerability. It was published on April 21, 2026 and has a CVSS 3.1 base score of 3.7 (LOW).

This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

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

How CyberStrike helps

Frequently asked questions

What is CVE-2026-40279?

CVE-2026-40279 is a low-severity vulnerability. It was published on April 21, 2026 and has a CVSS 3.1 base score of 3.7 (LOW).

How severe is CVE-2026-40279?

This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-40279?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-40279?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-40279 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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