CVE-2026-21878: Bacnetstack Bacnet Stack

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.5.0.rc3, a vulnerability has been discovered in BACnet Stack's file writing functionality where there is no validation of user-provided file paths, allowing attackers to write files to arbitrary directories. This affects apps/readfile/main.c and ports/posix/bacfile-posix.c. This vulnerability is fixed in 1.5.0.rc3.

Affected products

• Bacnetstack Bacnet Stack: version 1.5.0 only

Published 2026-02-13. Last modified 2026-06-17.