SecuriTricks - CVE-2026-40279

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.

Product(s) Impacted

Vendor	Product	Versions
Bacnet	Bacnet Stack	*

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-758

Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

The product uses an API function, data structure, or other entity in a way that relies on properties that are not always guaranteed to hold for that entity.

*CPE(s)

Affected systems and software identified for this CVE.

Type	Vendor	Product	Version	Update	Edition	Language	Software Edition	Target Software	Target Hardware	Other Information
a	bacnet	bacnet_stack	/	/	/	/	/	/	/	/

References

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

CVSS Score

3.7 / 10

CVSS Data - 3.1

Attack Vector: NETWORK
Attack Complexity: HIGH
Privileges Required: NONE
Scope: UNCHANGED
Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

View Vector String

Timeline

Published: April 21, 2026, 5:16 p.m.
Last Modified: April 22, 2026, 9:24 p.m.

Status : Awaiting Analysis

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

[email protected]

CVE-2026-40279