CVE-2026-11771: 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 wr

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-11771 is a high-severity flaw (CVSS 7.5) affecting openvpn. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-121, CWE-193, CWE-787
Published	2026-07-30
Last modified	2026-08-05

Publisher (CNA): OpenVPN Inc. · Vendor: openvpn

Last updated 2026-08-05 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-30 17:16 UTCPublished CVE record published
2026-08-05 19:38 UTCUpdated Record last modified

openvpn openvpn UPGRADE

Affected: >= 2.1.0 and < 2.6.21 · >= 2.7 and < 2.7.5

Fixed in: 2.6.21, 2.7.5

Safe to downgrade to: a release before 2.1.0

1. Check installed version

apt-cache policy openvpn || rpm -q openvpn || openvpn --version

2. UPGRADE to 2.6.21 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openvpn

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openvpn

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.1.0 (Debian / Ubuntu)

apt-cache madison openvpn sudo apt install openvpn=<VERSION_BEFORE_2.1.0> sudo apt-mark hold openvpn

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list openvpn sudo dnf downgrade openvpn-<VERSION_BEFORE_2.1.0> sudo dnf versionlock add openvpn

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-11771?

openvpn: upgrade to 2.6.21, 2.7.5. Exact commands for each OS are on this page.

Is CVE-2026-11771 being exploited?

CVE-2026-11771 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-11771 affect?

CVE-2026-11771 affects openvpn. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-11771?

Priority 39/100. High severity; Remotely exploitable, no login, no user action

Software pages

OpenVPN vulnerabilities

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References

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