Low severity3.7NVD Advisory· Published Apr 21, 2026· Updated Apr 27, 2026
CVE-2026-40279
CVE-2026-40279
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.
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Affected products
2cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*range: <1.4.3
- (no CPE)range: <1.4.3
Patches
Vulnerability mechanics
References
1- github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxvnvdExploitMitigationVendor Advisory
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