CVE-2026-21870

MEDIUM

5.5

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.

CVE Details

CVSS v3.1 Score5.5

SeverityMEDIUM

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

Attack VectorLOCAL

ComplexityLOW

Privileges RequiredNONE

User InteractionREQUIRED

Published2/13/2026

Last Modified2/18/2026

Sourcenvd

Honeypot Sightings0

Affected Products

bacnetstack:bacnet_stack

Weaknesses (CWE)

CWE-193

References

https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465(security-advisories@github.com)

https://github.com/bacnet-stack/bacnet-stack/pull/1196(security-advisories@github.com)

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx(security-advisories@github.com)

IOC Correlations

No correlations recorded

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