Buffer Overflow Vulnerability in BACnet Protocol Stack Library by BACnet
CVE-2026-21870
5.5MEDIUM
What is CVE-2026-21870?
The BACnet Protocol Stack library experiences a vulnerability characterized by an off-by-one stack-based buffer overflow within the ubasic interpreter. This issue arises in versions up to 1.5.0.rc2, where processing string literals exceeding the buffer limit can lead to application crashes due to improper null termination handling in the tokenizer_string function. Specifically, the function attempts to write a null byte at dest[40] despite the actual buffer size being limited to 40, effectively causing a stack overflow and resulting in a SIGABRT signal.
Affected Version(s)
bacnet-stack <= 1.4.2 <= 1.4.2
bacnet-stack >= 1.5.0.rc1, <= 1.5.0.rc2 <= 1.5.0.rc1, 1.5.0.rc2