{"id":"EUVD-2026-28789","revision":null,"records":[{"revision":"3f68229716074fe59d2e4933accbdf84","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-41070","aliases":[],"title":"openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access","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.","state":0,"publishedAt":"2026-05-08T15:14:46.186+00:00","modifiedAt":"2026-05-08T16:05:34.531+00:00","affected":[{"ecosystem":"Vendor product","name":"openvpn-auth-oauth2","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"jkroepke\",\n                    \"product\": \"openvpn-auth-oauth2\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 1.26.3, < 1.27.3\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","score":10,"severity":"CRITICAL"}],"references":["https://github.com/jkroepke/openvpn-auth-oauth2/security/advisories/GHSA-246w-jgmq-88fg","https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-41070","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-41070","identifiers":["CVE-2026-41070"]},"retained":false,"historicalAffected":[]},{"revision":"69902b5b54ea4cecb9517bd53784dcb3","observedAt":"2026-11-07T09:27:41.673+00:00","statement":{"source":"euvd","id":"EUVD-2026-28789","aliases":["CVE-2026-41070","GHSA-246w-jgmq-88fg"],"title":"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 p…","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.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","score":10,"severity":null}],"references":["https://github.com/jkroepke/openvpn-auth-oauth2/security/advisories/GHSA-246w-jgmq-88fg","https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-28789","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"May 8, 2026, 3:14:46 PM","dateUpdated":"May 8, 2026, 4:05:34 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-28789","identifiers":["EUVD-2026-28789","CVE-2026-41070","GHSA-246w-jgmq-88fg"]},"retained":false,"historicalAffected":[]},{"revision":"0f2e24ee4be947e4899fa11cf875bddf","observedAt":"2026-10-27T10:10:07.342+00:00","statement":{"source":"nvd","id":"CVE-2026-41070","aliases":[],"title":"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 p…","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.","state":0,"publishedAt":"2026-05-08T16:16:11.03+00:00","modifiedAt":"2026-10-26T18:10:00.173+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","score":10,"severity":"CRITICAL"}],"references":["https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2","https://github.com/jkroepke/openvpn-auth-oauth2/security/advisories/GHSA-246w-jgmq-88fg"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-41070","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-287"],"productCriteria":[],"sourceDates":{"published":"2026-05-08T16:16:11.030","lastModified":"2026-10-26T18:10:00.173"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-41070","identifiers":["CVE-2026-41070"]},"retained":false,"historicalAffected":[]},{"revision":"8f04bd3e6c5a4680aff49ccfe38e5364","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-246w-jgmq-88fg","aliases":["CVE-2026-41070","GO-2026-4963"],"title":"openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access","description":"# Summary\n\nWhen `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.\n\n# Impact\n\n**Authentication bypass — any VPN client that does not advertise WebAuth/SSO support (`IV_SSO=webauth`) is granted full network access without completing OIDC authentication.**\n\nThis affects only deployments running the **experimental plugin mode** in versions 1.26.3 through 1.27.2. The default and recommended deployment via the management interface is **not affected**.\n\nAn unauthenticated attacker can connect to the OpenVPN server using any standard OpenVPN client that does not support webauth (e.g., the Linux `openvpn` CLI). The plugin correctly issues a `client-deny` command via the management interface, but returns `OPENVPN_PLUGIN_FUNC_SUCCESS` (status=0) to OpenVPN. Because the `auth_control_file` content is only consulted when the plugin returns `FUNC_DEFERRED`, OpenVPN interprets status=0 as \"authentication passed\" and admits the client — granting full access to the internal network behind the VPN.\n\n\n## Root Cause\n\nIn `lib/openvpn-auth-oauth2/openvpn/handle.go`, the `ClientAuthDeny` branch of `handleAuthUserPassVerify` wrote `\"0\"` (deny) to the `auth_control_file` but returned `OPENVPN_PLUGIN_FUNC_SUCCESS`. OpenVPN only reads the `auth_control_file` when the plugin returns `FUNC_DEFERRED`; a synchronous `FUNC_SUCCESS` return is treated as immediate approval regardless of file contents.\n\n**Before fix:**\n```go\ncase management.ClientAuthDeny:\n    // ... writes \"0\" to auth_control_file ...\n    if err := openVPNClient.WriteToAuthFile(\"0\"); err != nil {\n        // only returned ERROR on write failure\n        return c.OpenVPNPluginFuncError\n    }\n    return c.OpenVPNPluginFuncSuccess  // ← BUG: OpenVPN sees this as \"auth passed\"\n```\n\n**After fix (commit [`36f69a6`](https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2)):**\n```go\ncase management.ClientAuthDeny:\n    // ... writes \"0\" to auth_control_file ...\n    if err := openVPNClient.WriteToAuthFile(\"0\"); err != nil {\n        logger.ErrorContext(p.ctx, \"write to auth file\", slog.Any(\"err\", err))\n    }\n    return c.OpenVPNPluginFuncError  // ← FIX: OpenVPN now correctly rejects the client\n```\n\n# Patches\n\nThis vulnerability is fixed in **v1.27.3**. Users of the experimental plugin mode should upgrade immediately.\n\n- **Fix commit:** [`36f69a6`](https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2)\n- **Fix PR:** [#829](https://github.com/jkroepke/openvpn-auth-oauth2/pull/829)\n\n# Workarounds\n\n- **Switch to standalone management client mode** (the default, non-plugin deployment). This mode is not affected by the vulnerability because authentication decisions are communicated entirely through the management interface protocol, not through the plugin return code.\n- **Restrict VPN access at the network level** to only clients known to support WebAuth/SSO (e.g., OpenVPN Connect 3+), although this is difficult to enforce reliably and is not recommended as a sole mitigation.","state":0,"publishedAt":"2026-04-22T14:28:11+00:00","modifiedAt":"2026-05-20T19:41:27.1835345+00:00","affected":[{"ecosystem":"Go","name":"github.com/jkroepke/openvpn-auth-oauth2","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.26.3"},{"kind":"fixed","version":"1.27.3"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"CRITICAL"}],"references":["https://github.com/jkroepke/openvpn-auth-oauth2/security/advisories/GHSA-246w-jgmq-88fg","https://nvd.nist.gov/vuln/detail/CVE-2026-41070","https://github.com/jkroepke/openvpn-auth-oauth2/pull/829","https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2","https://github.com/OpenVPN/openvpn/blob/master/include/openvpn-plugin.h.in","https://github.com/OpenVPN/openvpn3/blob/master/doc/webauth.md","https://github.com/jkroepke/openvpn-auth-oauth2","https://github.com/jkroepke/openvpn-auth-oauth2/releases/tag/v1.27.3"],"sourceUrl":"https://github.com/advisories/GHSA-246w-jgmq-88fg","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-246w-jgmq-88fg","identifiers":["GHSA-246w-jgmq-88fg","CVE-2026-41070","GO-2026-4963"]},"retained":false,"historicalAffected":[]},{"revision":"6f5915cfd7334bbbb4736f236a057ce1","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-4963","aliases":["CVE-2026-41070","GHSA-246w-jgmq-88fg"],"title":"openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access in github.com/jkroepke/openvpn-auth-oauth2","description":"openvpn-auth-oauth2 returns FUNC_SUCCESS on client-deny, allowing unauthenticated VPN access in github.com/jkroepke/openvpn-auth-oauth2","state":0,"publishedAt":"2026-05-20T19:07:16+00:00","modifiedAt":"2026-05-20T19:30:11.5436337+00:00","affected":[{"ecosystem":"Go","name":"github.com/jkroepke/openvpn-auth-oauth2","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.26.3"},{"kind":"fixed","version":"1.27.3"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/jkroepke/openvpn-auth-oauth2/security/advisories/GHSA-246w-jgmq-88fg","https://nvd.nist.gov/vuln/detail/CVE-2026-41070","https://github.com/jkroepke/openvpn-auth-oauth2/commit/36f69a6c67c1054da7cbfa04ced3f0555127c8f2","https://github.com/jkroepke/openvpn-auth-oauth2/pull/829","https://github.com/OpenVPN/openvpn/blob/master/include/openvpn-plugin.h.in","https://github.com/OpenVPN/openvpn3/blob/master/doc/webauth.md","https://github.com/jkroepke/openvpn-auth-oauth2/releases/tag/v1.27.3"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-4963","license":"OSV · upstream source license applies","key":"osv:GO-2026-4963","identifiers":["GO-2026-4963","CVE-2026-41070","GHSA-246w-jgmq-88fg"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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