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OpenvpnApplication

CVE-2026-13122

MEDIUM · 5.3 CVSS v3.1 Published 2026-07-06
Fix available
A fix is available. Upgrade to 2.6.21 / 2.7.5 or later.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable Zero-click 6 weeks old

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 · unedited
OpenVPN version 2.6.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows remote attackers to cause a denial of service via a malformed authentication token that triggers a reachable assertion when external-auth is enabled

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 · moderate confidence

OpenVPN versions 2.6.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 contain a denial-of-service vulnerability where a remote attacker can send a malformed authentication token that triggers a reachable assertion failure, causing the VPN service to crash or become unavailable. This exploit is only possible when the external-authentication feature is enabled.

MitigationDisable external-auth if not required, or upgrade to a patched version of OpenVPN beyond 2.6.20/2.7.4 once available. Verify external-auth configuration and implement rate limiting on authentication endpoints as a defense-in-depth measure.

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
Affected:>= 2.6.0, < 2.6.21>= 2.7, < 2.7.5

CVSS 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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed OpenVPN version
    Run 'openvpn --version' or 'openvpn2 --version' to retrieve the installed binary version
    Affected if Version is 2.6.0 through 2.6.20, or 2.7.0 through 2.7.4 (including alpha/beta variants)
  2. Verify external-auth plugin is loaded
    Inspect the OpenVPN server configuration file (typically /etc/openvpn/server.conf) and look for lines containing 'plugin' that reference an external authentication script or shared object, or look for 'auth-user-pass-verify' directive
    Affected if The configuration contains a plugin directive loading an external auth module, or uses 'auth-user-pass-verify' to invoke an external script
  3. Confirm external-auth is actively used
    Check running OpenVPN process with 'ps aux | grep openvpn' and review any startup scripts or systemd unit files for external authentication enablement
    Affected if External authentication is actively enabled in the running configuration
  4. Identify configuration file location
    Locate all OpenVPN configuration files: check /etc/openvpn/, /etc/openvpn/server/, /etc/openvpn/client/, or custom paths specified in systemd service files
    Affected if Configuration files exist and external-auth is present

A system is affected if it runs a vulnerable OpenVPN version (2.6.0-2.6.20 or 2.7.x through 2.7.4) AND has external authentication (external auth plugin or auth-user-pass-verify) enabled in its active configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to 2.6.21 / 2.7.5 or later
Fixed in 2.6.212.7.5
Interim mitigation

Disable external-auth if not required, or upgrade to a patched version of OpenVPN beyond 2.6.20/2.7.4 once available. Verify external-auth configuration and implement rate limiting on authentication endpoints as a defense-in-depth measure.

Recommended fix High confidence

OpenVPN 2.6.21 or later for 2.6.x branch; OpenVPN 2.7.5 or later for 2.7.x branch

  1. 1. Check current OpenVPN version: openvpn --version
  2. 2. Backup all OpenVPN configuration files in /etc/openvpn/
  3. 3. Update your package repository: sudo apt update (Debian/Ubuntu) or sudo yum check-update (RHEL/CentOS)
  4. 4. Install the fixed version: sudo apt install openvpn=2.6.21-1 (Debian/Ubuntu) or sudo yum install openvpn-2.6.21 (RHEL/CentOS)
  5. 5. If using 2.7.x branch, install openvpn=2.7.5 or openvpn-2.7.5 respectively
  6. 6. Restart the OpenVPN service: sudo systemctl restart openvpn@<config-name> or sudo systemctl restart openvpn
  7. 7. Verify the installed version: openvpn --version
  8. 8. Test VPN connectivity to confirm normal operation
Caveat Minor - this is a security patch release with no documented breaking changes; always review release notes before upgrading in production

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Openvpn Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-13122 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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