What is CVE-2026-21870?

CVE-2026-21870 is a medium-severity vulnerability in Bacnet-stack, classified under Off-by-one Error. CVSS score: 5.5/10. Published 2026-02-13.

How severe is CVE-2026-21870?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Bacnet-stack

CVE-2026-21870

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 ca…

EPSS: 0.000 (0.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

Affected products

Bacnet-stack — versions <= 1.4.2, >= 1.5.0.rc1, <= 1.5.0.rc2

Weakness classification (CWE)

CWE-193 — Off-by-one Error

References

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx (x_refsource_CONFIRM)
https://github.com/bacnet-stack/bacnet-stack/pull/1196 (x_refsource_MISC)
https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-21870?: CVE-2026-21870 is a medium-severity vulnerability in Bacnet-stack, classified under Off-by-one Error. CVSS score: 5.5/10. Published 2026-02-13.
How severe is CVE-2026-21870?: Medium severity. CVSS v3 base score is 5.5 out of 10.