CVE-2026-41070Network attack vector

Unauthenticated VPN access via incorrect plugin return

Published May 8, 2026 · Updated May 8, 2026

Authentication bypass in openvpn-auth-oauth2 1.26.3 through 1.27.2 allows remote attackers to gain full VPN network access. The ClientAuthDeny branch in handleAuthUserPassVerify writes a denial to auth_control_file but returns OPENVPN_PLUGIN_FUNC_SUCCESS, which OpenVPN treats as approval. Exploitation requires experimental Linux plugin mode and a client without WebAuth support; the default management-interface mode is unaffected.

CVSS severity10.0
Critical
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in openvpn-auth-oauth2 1.26.3 through 1.27.2 allows remote attackers to gain full VPN network access. The ClientAuthDeny branch in handleAuthUserPassVerify writes a denial to auth_control_file but returns OPENVPN_PLUGIN_FUNC_SUCCESS, which OpenVPN treats as approval. Exploitation requires experimental Linux plugin mode and a client without WebAuth support; the default management-interface mode is unaffected.

The record

CVE
CVE-2026-41070
Published
May 8, 2026
Updated
May 8, 2026
Vendor
Jan-Otto Kröpke
Product
openvpn-auth-oauth2
Classifications
CWE-287, T1133
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 8, 2026CVE publishedPublication date reported by the CVE source.
  2. May 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.26.3, < 1.27.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Jan-Otto Kröpke · openvpn-auth-oauth2version=>= 1.26.3, < 1.27.3

Published CVSS scores

10.0GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1133External Remote Services

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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