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Improper AuthenticationWeakness · CWE-287

CVE-2026-41070

CRITICAL · 10.0 CVSS v3.1 Published 2026-05-08
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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-auth-oauth2 is a plugin/management interface client for OpenVPN server to handle an OIDC based single sign-on (SSO) auth flows. From version 1.26.3 to before version 1.27.3, when openvpn-auth-oauth2 is deployed in the experimental plugin mode (shared library loaded by OpenVPN via the plugin directive), clients that do not support WebAuth/SSO (e.g., the openvpn CLI on Linux) are incorrectly admitted to the VPN despite being denied by the authentication logic. The default management-interface mode is not affected because it does not use the OpenVPN plugin return-code mechanism. This issue has been patched in version 1.27.3.

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 confidence

In openvpn-auth-oauth2 versions 1.26.3 through 1.27.2, the plugin mode (shared library loaded via OpenVPN's plugin directive) incorrectly admits clients that cannot handle WebAuth/SSO authentication (like the openvpn CLI on Linux) despite the authentication logic denying them. This occurs because the plugin return-code mechanism improperly handles non-SSO-capable clients, allowing authentication bypass. The management-interface mode is unaffected as it doesn't use the plugin return-code mechanism.

MitigationUpgrade openvpn-auth-oauth2 to version 1.27.3 or later. If immediate upgrade is not possible, consider switching from plugin mode to management-interface mode as a workaround.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

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. Identify openvpn-auth-oauth2 installation
    Check if openvpn-auth-oauth2 is installed on the system. Look for the binary or shared library (typically at /usr/local/bin/openvpn-auth-oauth2 or /usr/lib/openvpn-auth-oauth2.so) or query the package manager if installed via packages.
    Affected if openvpn-auth-oauth2 is not installed, the system is not vulnerable to this CVE.
  2. Determine installed version
    Run 'openvpn-auth-oauth2 --version' or check the package version to identify the exact version number of openvpn-auth-oauth2.
    Affected if The version is between 1.26.3 and 1.27.2 inclusive, the plugin is in the affected version range.
  3. Identify deployment mode
    Examine the OpenVPN server configuration file (typically /etc/openvpn/server.conf) to determine if the plugin mode or management-interface mode is in use. Look for a 'plugin' directive pointing to the openvpn-auth-oauth2 shared library for plugin mode, or 'management' directive for management-interface mode.
    Affected if Plugin mode is configured (via the 'plugin' directive loading the OAuth2 shared library), the authentication bypass vulnerability is present. If only management-interface mode is used, this specific CVE does not apply.

The environment is affected if openvpn-auth-oauth2 version 1.26.3 through 1.27.2 is installed AND the plugin mode (shared library via OpenVPN plugin directive) is being used for authentication.

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
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade openvpn-auth-oauth2 to version 1.27.3 or later. If immediate upgrade is not possible, consider switching from plugin mode to management-interface mode as a workaround.

Recommended fix High confidence

1.27.3

  1. 1. Identify the current version of openvpn-auth-oauth2 currently deployed by checking the binary or package version.
  2. 2. Stop the OpenVPN service to ensure no active VPN connections during the upgrade.
  3. 3. Upgrade openvpn-auth-oauth2 to version 1.27.3 or later. Use the appropriate package manager or build from source for your distribution (e.g., apt-get install, yum install, or compile from the official repository).
  4. 4. Verify the upgraded version matches 1.27.3 or newer.
  5. 5. Restart the OpenVPN service to load the patched plugin.
  6. 6. Test VPN authentication to confirm the fix is working - both SSO-capable clients and non-SSO clients should be handled correctly according to policy.

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

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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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-2026-41070 in production — separate from our analysis above.

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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