What is CVE-2021-3547?

CVE-2021-3547 is a high-severity vulnerability in Openvpn, classified under Authentication Bypass by Primary Weakness. CVSS score: 7.4/10. Published 2021-07-12.

How severe is CVE-2021-3547?

High severity. CVSS v3 base score is 7.4 out of 10.

Vulnerability in Openvpn

CVE-2021-3547

OpenVPN 3 Core Library version 3.6 and 3.6.1 allows a man-in-the-middle attacker to bypass the certificate authentication by issuing an unrelated server certificate using the same hostname found in the verify-x509-name option in a client configuration.

Published 2021-07-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.012 (68.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Openvpn — versions 3.6, 3.6.1
Openvpn 3 Core Library — versions 3.6 and 3.6.1

Weakness classification (CWE)

References

community.openvpn.net/openvpn/wiki/SecurityAnnouncements (Vendor Advisory)
community.openvpn.net/openvpn/wiki/CVE-2021-3547 (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-3547?: CVE-2021-3547 is a high-severity vulnerability in Openvpn, classified under Authentication Bypass by Primary Weakness. CVSS score: 7.4/10. Published 2021-07-12.
How severe is CVE-2021-3547?: High severity. CVSS v3 base score is 7.4 out of 10.