OpenvpnApplication
CVE-2026-11604
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn 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).
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceAn incorrect buffer size calculation in the epoch key generator of OpenVPN ovpn-dco-win (versions 2.0.0-2.8.3) allows a remote authenticated peer to send crafted data packets that trigger a heap-based buffer overflow, leading to kernel memory corruption and system crash (denial of service).
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
OpenvpnApplication
>= 2.0.0, <= 2.8.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify ovpn-dco-win driver is installedOpen PowerShell as Administrator and run: Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\ovpn-dco-win' -ErrorAction SilentlyContinue | Select-Object DisplayName, Version, StartAffected if The driver is not installed or the registry key does not exist - not affected. If installed, note the Version value for next step.
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Check ovpn-dco-win driver versionReview the Version value from the previous step. Compare it against the affected range: 2.0.0 through 2.8.3Affected if Version falls within 2.0.0 to 2.8.3 inclusive - potentially affected. Version 2.8.4 or later, or version earlier than 2.0.0, is not in the affected range.
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Confirm OpenVPN is using ovpn-dco data channel offloadCheck OpenVPN configuration files (typically in C:\Program Files\OpenVPN\config\ or C:\ProgramData\OpenVPN\config\) for the 'data-channel-offload' directive or dco related settings in .ovpn configuration filesAffected if The driver is installed and in vulnerable version range, AND data-channel-offload or dco variant is explicitly enabled in active OpenVPN configuration - likely affected. If dco is not enabled, the epoch key generator may not be in active use.
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Verify remote access VPN service is exposedCheck if the OpenVPN server service is running and listening on UDP/TCP ports (commonly 1194). Run: netstat -an | findstr '1194' or review firewall rules for inbound VPN connectionsAffected if An authenticated remote peer can send packets to the VPN server. If the server does not accept remote connections, the attack surface is not present.
System is affected only if ovpn-dco-win driver versions 2.0.0-2.8.3 is installed, data-channel-offload feature is enabled in the OpenVPN configuration, and the system accepts authenticated remote VPN connections.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade ovpn-dco-win to version 2.8.4 or later where the buffer size calculation is corrected. If immediate upgrade is not feasible, restrict VPN access to trusted authenticated users only to reduce attack surface.
Fix this in Openvpn
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-11604 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-11604 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data