CVE-2026-11604: An incorrect buffer size calculation in the epoch key generator in OpenVPN ovpn-dco-win version 2.0.0 through

Routine

MEDIUM 6.5UPGRADE

CVE-2026-11604 is a medium-severity flaw (CVSS 6.5) affecting ovpn-dco-win. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An incorrect buffer size calculation in the epoch key generator in OpenVPN ovpn-dco-win version 2.0.0 through 2.8.3 allows a remote authenticated peer to trigger a heap-based buffer overflow and kernel memory corruption via a crafted data packet, resulting in a system crash (denial of service).

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-122, CWE-131, CWE-787
Published	2026-06-10
Last modified	2026-09-24

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

Last updated 2026-09-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-10 22:16 UTCPublished CVE record published
2026-09-24 14:39 UTCUpdated Record last modified

openvpn ovpn-dco-win UPGRADE

Affected: >= 2.0.0 and <= 2.8.3

Fixed in: newer than 2.8.3

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy ovpn-dco-win || rpm -q ovpn-dco-win || ovpn-dco-win --version

2. UPGRADE to newer than 2.8.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade ovpn-dco-win

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ovpn-dco-win

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 2.0.0 (Debian / Ubuntu)

apt-cache madison ovpn-dco-win sudo apt install ovpn-dco-win=<VERSION_BEFORE_2.0.0> sudo apt-mark hold ovpn-dco-win

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

dnf --showduplicates list ovpn-dco-win sudo dnf downgrade ovpn-dco-win-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add ovpn-dco-win

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-2026-11604?

ovpn-dco-win: upgrade to newer than 2.8.3. Exact commands for each OS are on this page.

Is CVE-2026-11604 being exploited?

CVE-2026-11604 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-2026-11604 affect?

CVE-2026-11604 affects ovpn-dco-win. Severity is medium (CVSS 6.5). An incorrect buffer size calculation in the epoch key generator in OpenVPN ovpn-dco-win version 2.0.0 through 2.8.3 allows a remote authenticated peer to trigger a heap-based buffer overflow and kernel memory corruption via a crafted data p

How urgent is CVE-2026-11604?

Priority 29/100. No elevated risk signals yet.

Software pages

OpenVPN vulnerabilities

References

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