CVE-2026-21870

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

13/02/2026

Last modified:

18/02/2026

Description

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.

Impact

Vector 3.x

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H CVSS v3.1 Severity and Metrics:

Base Score: 5.50 MEDIUM
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector (AV): Local
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): Required
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): High

Base Score 3.x

5.50

Severity 3.x

MEDIUM

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:a:bacnetstack:bacnet_stack::::::::		1.4.2 (including)
cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc1::::::
cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc2::::::

To consult the complete list of CPE names with products and versions, see this page

CVE-2026-21870

Description

Impact

Vulnerable products and versions

References to Advisories, Solutions, and Tools