CVE-2026-11771

Publication date 3 July 2026

Last updated 7 August 2026

Ubuntu priority

Cvss 3 Severity Score

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

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
openvpn	26.04 LTS resolute	Fixed 2.7.0-1ubuntu1.2
	25.10 questing	Ignored end of life, was needs-triage
	24.04 LTS noble	Fixed 2.6.19-0ubuntu0.24.04.3
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

mdeslaur

introduced by: https://github.com/OpenVPN/openvpn/commit/6e010d4824b7251d817cf1770e80f186000b99ae jammy and earlier already have an adequate check, so are not vulnerable.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
openvpn	Upstream: 04309bf

Severity score breakdown

CVSS version:

Base score 7.0 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	High
Attack requirements	Present
Privileges required	None
User interaction	Passive
Vulnerable system - Confidentiality impact	None
Vulnerable system - Integrity impact	None
Vulnerable system - Availability impact	High
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	High

Scores

Parameter	Value
Base score	7.0 · High
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

Base score 7.5 · High