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CVE-2026-40279

LOW · CVSS 3.7 EPSS 0.04% Public Exploit

Source: NVD + CISA KEV + EPSS · Published: 2026-04-21 · Last synced: 2026-05-18

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Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

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CVE
CVE-2026-40279
Severity
LOW
CVSS
3.7
EPSS
0.04%

Original 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.