CVE-2026-40279: BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`
Affected: bacnet-stack · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 15% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- bacnet-stack · bacnet-stack< 1.4.3
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Weakness
- Reliance on Undefined, Unspecified, or Implementation-Defined Behavior · Input Validation and Logic
- Vendor
- bacnet-stack
- Published
- April 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-40279 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.