What is CVE-2021-4234?

CVE-2021-4234 is a high-severity vulnerability in Openvpn Access Server, classified under CWE-406. CVSS score: 7.5/10. Published 2022-07-06.

How severe is CVE-2021-4234?

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

Vulnerability in Openvpn Access Server

CVE-2021-4234

OpenVPN Access Server 2.10 and prior versions are susceptible to resending multiple packets in a response to a reset packet sent from the client which the client again does not respond to, resulting in a limited amplification attack.

Published 2022-07-06 · last modified 2026-06-17.

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:N/A:H.

EPSS exploit prediction

EPSS: 0.009 (58.8th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: +0.000

Affected products

Openvpn Access Server
Openvpn Access Server — versions 2.10 and prior version

Weakness classification (CWE)

CWE-406

References

openvpn.net/vpn-server-resources/release-notes/ (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-4234?: CVE-2021-4234 is a high-severity vulnerability in Openvpn Access Server, classified under CWE-406. CVSS score: 7.5/10. Published 2022-07-06.
How severe is CVE-2021-4234?: High severity. CVSS v3 base score is 7.5 out of 10.