CVE-2026-21870
MEDIUMCVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
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.
Analysis
The BACnet Protocol Stack library versions 1.4.2 and earlier contain an off-by-one buffer overflow in the ubasic interpreter's string tokenizer that crashes the application when processing oversized string literals. Public exploit code exists for this vulnerability, which affects any system running vulnerable versions of the BACnet Stack or Stack Overflow products. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.
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External POC / Exploit Code
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