CVE-2026-21870

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.

CVSS v3 5.5 MEDIUM

5.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 1.8 / Impact : 3.6

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465	Patch
https://github.com/bacnet-stack/bacnet-stack/pull/1196	Patch
https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx	Vendor Advisory Exploit

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:bacnetstack:bacnet_stack::::::::
	cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc1::::::
	cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc2::::::

History

No history.

Information

Published : 2026-02-13 18:16

Updated : 2026-02-18 18:49

NVD link : CVE-2026-21870

Mitre link : CVE-2026-21870

CVE.ORG link : CVE-2026-21870

JSON object : View

Products Affected

bacnetstack

bacnet_stack

CWE

CWE-193

Off-by-one Error

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