Vulnerability 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.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Bacnetstack | Bacnet Stack | < 1.4.3 |
Related Weaknesses (CWE)
References
- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-ExploitMitigationVendor Advisory
- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-ExploitMitigationVendor Advisory
FAQ
What is CVE-2026-40279?
CVE-2026-40279 is a vulnerability with a CVSS score of 3.7 (LOW). 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 u...
How severe is CVE-2026-40279?
CVE-2026-40279 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40279?
Check the references section above for vendor advisories and patch information. Affected products include: Bacnetstack Bacnet Stack.