Vulnerability · Published Feb 13, 2026 · Assigned by GitHub_M
CVE-2026-21870The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string
Medium 5.5
In plain English
A medium-severity security flaw in bacnet-stack from bacnet-stack. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| bacnet-stack | bacnet-stack | <= 1.4.2>= 1.5.0.rc1, <= 1.5.0.rc2 |
Weakness: CWE-193 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H