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CVE-2026-40279

low

BACnet Stack is a BACnet open source protocol stack C library for embedded systems.

Vendor / product: Bacnetstack — bacnet stack

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
3.7
3.7 (CVSS v3.1)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Severity source: NVD CVSS v3.1 (security-advisories@github.com)
Timeline (UTC)
Published: 2026-04-21 17:16
Modified: 2026-11-11 23:10
NVD status: Analyzed
Last synced 3 hours ago
Verified against the source API 2026-11-11 23:12 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

bacnetstack / bacnet_stack <1.4.3

Weakness classification (CWE)

CWE-758

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

Vendor advisory: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv
Vendor advisory: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv
Patch / mitigation: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv
Patch / mitigation: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv

References

Data sources

NVD CVE API 2.0 — fetched 2026-11-11 23:12 UTC · record ↗

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