CVE-2026-40279
Last modified
CVE-2026-40279 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. 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. EPSS estimates a 0.24% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Bacnetstack | Bacnet Stack | < 1.4.3 |
References
- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxvExploit, Mitigation, Vendor Advisory
- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxvExploit, Mitigation, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
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