CVE-2026-21878 — HIGH (7.5)

Vulnerability Description

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.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

HIGH

Availability

NONE

Affected Products

Vendor	Product	Versions
Bacnetstack	Bacnet Stack	1.5.0

Related Weaknesses (CWE)

CWE-22

References

FAQ

What is CVE-2026-21878?

CVE-2026-21878 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 ...

How severe is CVE-2026-21878?

CVE-2026-21878 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-21878?

Check the references section above for vendor advisories and patch information. Affected products include: Bacnetstack Bacnet Stack.