Is CVE-2026-40279 in the CISA KEV catalog?

No. CVE-2026-40279 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40279?

CVE-2026-40279 has a CVSS v3 base score of 3.7 (LOW).

What is the EPSS score for CVE-2026-40279?

CVE-2026-40279 has an EPSS score of 0.24% (15th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40279?

Upgrade bacnet stack to 1.4.3 or later.

CVE & CISA-KEV Catalog

CVE-2026-40279

LOW

3.7

CVSS v3

NVD

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.

CWE-758

How to fix

Remediation Available

bacnet stackNVD

Affected:< 1.4.3Fixed in:1.4.3CVE-2026-40279derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

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

Exploit Intelligence

0.24%probability of exploitation in 30 days

15thpercentile

Low risk: more likely to be exploited than 15% of all known CVEs.

References

Exploit1

github.com

Embed a live status badge for CVE-2026-40279

Markdown

[![CVE-2026-40279](https://tridentstack.com/cve/badge/CVE-2026-40279.svg)](https://tridentstack.com/cve/CVE-2026-40279)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-40279"><img src="https://tridentstack.com/cve/badge/CVE-2026-40279.svg" alt="CVE-2026-40279"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-27.