CVE-2026-21870

MEDIUM EPSS 15.0%
Published Feb 13, 20264mo ago · Modified Jun 17, 20262w ago
5.5 CVSS 3.1
Medium
Find Similar
Published Feb 13, 2026 4mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required None
User Interaction Required
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
15.0% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-193

Affected Products 3

VendorProductVersionRange
bacnetstackbacnet_stack* ≤1.4.2
bacnetstackbacnet_stack1.5.0any
bacnetstackbacnet_stack1.5.0any

References 3

  • github.com https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465
    Patch
  • github.com https://github.com/bacnet-stack/bacnet-stack/pull/1196
    Patch
  • github.com https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx
    ExploitVendor Advisory

Remediation

  • github.com https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465
    Patch
  • github.com https://github.com/bacnet-stack/bacnet-stack/pull/1196
    Patch