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    CVE-2026-40279

    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.

    Published:Apr 21, 2026
    Last Modified:Apr 27, 2026
    EPS:Apr 21, 2026
    EPSS Score:0.00044
    CVSS Score:3.7

    Affected Products

    Vendor
    Bacnetstack
    Product
    Bacnet Stack

    Exploits

    https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxvhttps://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High