# CVE-2026-41070: openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access

> Attackers can bypass authentication and gain unauthenticated VPN access when using the experimental plugin mode in openvpn-auth-oauth2.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 8 May 2026
- **Also known as:** DEBIAN-CVE-2026-41070, GHSA-246w-jgmq-88fg, GO-2026-4963, UBUNTU-CVE-2026-41070

## What is CVE-2026-41070?

CVE-2026-41070 is a critical authentication bypass vulnerability in jkroepke openvpn-auth-oauth2, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-41070?

3 open source packages ship an affected version, including github.com/jkroepke/openvpn-auth-oauth2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/jkroepke/openvpn-auth-oauth2` | Go | From 1.26.3 | 1.27.3 |
| `github.com/jkroepke/openvpn-auth-oauth2` | Go | From 1.26.3 | 1.27.3 |
| `github.com/jkroepke/openvpn-auth-oauth2` | Go | From 1.26.3 | 1.27.3 |

## How do I fix CVE-2026-41070?

Upgrade github.com/jkroepke/openvpn-auth-oauth2 to 1.27.3 or later.

## Is CVE-2026-41070 being exploited?

There is no known exploitation of CVE-2026-41070 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-41070 and fix it if it is affected.

What it is: CVE-2026-41070 is a critical authentication bypass vulnerability in jkroepke openvpn-auth-oauth2, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-41070 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/jkroepke/openvpn-auth-oauth2 (Go): affected from 1.26.3; fixed in 1.27.3
- github.com/jkroepke/openvpn-auth-oauth2 (Go): affected from 1.26.3; fixed in 1.27.3
- github.com/jkroepke/openvpn-auth-oauth2 (Go): affected from 1.26.3; fixed in 1.27.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-41070/ (Markdown: https://insights.sbomify.com/CVE-2026-41070/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41070
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41070
- OSV: https://osv.dev/vulnerability/CVE-2026-41070

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-41070/
Summaries are generated and may contain mistakes; the official description above is the record.