CVE-2021-4234

Name: CVE-2021-4234
Creator: NVD / NIST
Published: 2022-07-06T20:15:08.127+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.76%

Last modified Jun 17, 2026

CVE-2021-4234 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 0.76% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.76%

50.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-406

Affected Software

Vendor	Product	Versions
Openvpn	Openvpn Access Server	< 2.11.0

References

https://openvpn.net/vpn-server-resources/release-notes/#openvpn-access-server-2-11-0Release Notes, Vendor Advisory
https://openvpn.net/vpn-server-resources/release-notes/#openvpn-access-server-2-11-0Release Notes, Vendor Advisory

Timeline

Published: Jul 6, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-4234?

How severe is CVE-2021-4234?

CVE-2021-4234 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.76% probability of exploitation in the next 30 days.

How do I fix CVE-2021-4234?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-4234?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST