CVE-2026-21870

Summary

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.

Affected Software

VendorProductVersion RangeStatus
bacnet-stackbacnet-stack<= 1.4.2affected
bacnet-stackbacnet-stack>= 1.5.0.rc1, <= 1.5.0.rc2affected

Weaknesses

  • CWE-193: CWE-193: Off-by-one Error

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References