What is CVE-2021-27891?

CVE-2021-27891 is a high-severity vulnerability in Microsoft Windows. CVSS score: 8.8/10. Published 2021-03-15.

How severe is CVE-2021-27891?

High severity. CVSS v3 base score is 8.8 out of 10.

Vulnerability in Microsoft Windows

CVE-2021-27891

SSH Tectia Client and Server before 6.4.19 on Windows have weak key generation. ConnectSecure on Windows is affected.

Published 2021-03-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.011 (64.5th percentile), scored 2026-10-21.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.011 · change: +0.000

Affected products

References

info.ssh.com/tectia-vulnerability-cve-2021-27891 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-27891?: CVE-2021-27891 is a high-severity vulnerability in Microsoft Windows. CVSS score: 8.8/10. Published 2021-03-15.
How severe is CVE-2021-27891?: High severity. CVSS v3 base score is 8.8 out of 10.