CVE-2026-40279 (GCVE-0-2026-40279)
Vulnerability from cvelistv5 – Published: 2026-04-21 16:29 – Updated: 2026-04-21 19:18
VLAI?
Title
BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`
Summary
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.
Severity ?
CWE
- CWE-758 - Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Assigner
References
| URL | Tags | ||||
|---|---|---|---|---|---|
|
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Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| bacnet-stack | bacnet-stack |
Affected:
< 1.4.3
|
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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