What is CVE-2026-21878?

CVE-2026-21878 is a high-severity vulnerability in Bacnet-Stack, classified under Path Traversal. CVSS score: 7.5/10. Published 2026-02-13.

How severe is CVE-2026-21878?

High severity. CVSS v3 base score is 7.5 out of 10.

Path Traversal in Bacnet-Stack

CVE-2026-21878

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.

Vulnerability class: Path Traversal (Directory Traversal)

EPSS: 0.004 (28.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

Affected products

Bacnet-stack — versions < 1.5.0.rc3
Bacnetstack Bacnet_stack — versions 1.5.0

Weakness classification (CWE)

CWE-22 — Path Traversal

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2026-21878?: CVE-2026-21878 is a high-severity vulnerability in Bacnet-Stack, classified under Path Traversal. CVSS score: 7.5/10. Published 2026-02-13.
How severe is CVE-2026-21878?: High severity. CVSS v3 base score is 7.5 out of 10.