What is CVE-2019-16871?

CVE-2019-16871 is a critical-severity vulnerability in Beckhoff Twincat, classified under Authentication Bypass by Spoofing. CVSS score: 9.8/10. Published 2019-12-19.

How severe is CVE-2019-16871?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Beckhoff Twincat

CVE-2019-16871

Beckhoff Embedded Windows PLCs through 3.1.4024.0, and Beckhoff Twincat on Windows Engineering stations, allow an attacker to achieve Remote Code Execution (as SYSTEM) via the Beckhoff ADS protocol.

Published 2019-12-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.053 (92.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 92nd percentile — 92.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.053 · newest: 0.053 · change: 0.000

Affected products

Beckhoff Twincat — versions 2.0, 3.1

Weakness classification (CWE)

CWE-290 — Authentication Bypass by Spoofing

References

www.ic4.be/2019/12/18/beckhoff-cve-2019-16871/ (Exploit, Third Party Advisory)
download.beckhoff.com/download/document/product-security/Advisories/advisory-20… (Vendor Advisory)

Frequently asked questions

What is CVE-2019-16871?: CVE-2019-16871 is a critical-severity vulnerability in Beckhoff Twincat, classified under Authentication Bypass by Spoofing. CVSS score: 9.8/10. Published 2019-12-19.
How severe is CVE-2019-16871?: Critical severity. CVSS v3 base score is 9.8 out of 10.