CVE•Published 2026-04-21•Modified 2026-04-27•0 articles on news•5 live references•NVD data

CVE-2026-40279Bacnetstack · Bacnet_stack

Vulnerability data via NVD (ingested)

CVSS v3.1

3.7

LOW

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

EPSS percentile

Exploit Prediction Scoring System · top 90% of all CVEs

Weaknesses (CWE)

CWE-758Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

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.

Timeline

Published 2026-04-21

Modified 2026-04-27

External references

NVD MITRE Exploit-DB trickest/cve VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-40279

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Bacnetstack Bacnet Stack"

All exposed Bacnetstack Bacnet Stack instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Bacnet Stack"

HTTP body or banner mentions "Bacnet Stack" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-40279