CVE-2021-4234 Denial of service in OpenVPN Access Server

High 7.5 Published 6 Jul 2022 Updated 3 Aug 2024

OpenVPN Access Server is vulnerable to a limited amplification attack via reset packets, potentially causing denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2021-4234?

CVE-2021-4234 is a high-severity denial of service vulnerability in OpenVPN Access Server, published on 6 Jul 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-406

Which versions are affected by CVE-2021-4234?

It affects 1 product.

Products include Openvpn Openvpn Access Server.

How do I fix CVE-2021-4234?

No fix has been published for CVE-2021-4234 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-4234 being exploited?

There is no known exploitation of CVE-2021-4234 in the wild and no public exploit code.

Sources

Also known as GHSA-qvww-9jm9-f3pm.