CVE-2026-40279: bacnet-stack · Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Affects bacnet-stackSource GCVE Database
Not known to be exploited · CVSS 3.7 Low : upgrade to 1.4.3 when convenient.
Data as of 12 Nov 2026, 01:33 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 3.7 |
|---|
- Patch
- Available – fixed in 1.4.3
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:LExploitation evidence
Disclosed: evidence found.
CVE published 21 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.
What to do
Upgrade bacnet-stack to 1.4.3.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| bacnet-stack bacnet-stack | Affected
| Fixed in
|
AI-suggested
Upgrade to bacnet-stack version 1.4.3 or later, where this vulnerability is fixed. No other mitigation is required as the issue is resolved in the official patch.
Description
CVE-2026-40279 is a vulnerability in the bacnet-stack open source BACnet protocol library for embedded systems. Versions prior to 1.4.3 contain a flaw in the decode_signed32() function, which reconstructs a 32-bit signed integer from four bytes using signed left shifts. When any byte has its highest bit set (≥ 0x80), this causes signed integer overflow, which is undefined behavior according to the C standard. This issue is fixed in version 1.4.3.