CVE-2026-11771 Memory corruption in OpenVPN

High 7.0 Published 30 Jul 2026 Updated 30 Jul 2026

Attackers can cause a crash in OpenVPN clients via a crafted NTLM response from a malicious proxy server due to an off-by-one buffer write.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2026-11771?

CVE-2026-11771 is a high-severity memory corruption vulnerability in OpenVPN, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

OpenVPN version 2.1.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows attackers via an off-by-one buffer write in the NTLM proxy authentication to potentially cause a crash via a crafted NTLM response from a malicious proxy server

Weakness: CWE-787, CWE-193, CWE-121

Which versions are affected by CVE-2026-11771?

It affects 1 product.

Products include Openvpn Openvpn.

How do I fix CVE-2026-11771?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-11771 being exploited?

There is no known exploitation of CVE-2026-11771 in the wild and no public exploit code.

Sources

Also known as ALPINE-CVE-2026-11771, DEBIAN-CVE-2026-11771, GHSA-v8ww-fhqp-9vff, UBUNTU-CVE-2026-11771.