{"id":"CVE-2026-63439","published":"2026-11-06T21:17:09.970","lastModified":"2026-11-09T14:17:22.053","description":"2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. Prior to 8.0.0, when AUTHENTICATION_GUARD=reverse-proxy-guard is enabled, ReverseProxyGuard::user() reads the default REMOTE_USER identity header, or a custom identity header selected by the AUTH_PROXY_HEADER_FOR_USER configuration setting, without confirming that the request originated from a configured trusted proxy. A remote client that can reach the application directly can forge the selected identity header and authenticate as an existing user, including an administrator, gaining access to stored 2FA secrets and account or application management functions. This issue is fixed in version 8.0.0.","cvssScore":9.8,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwes":["CWE-287"],"vendors":[],"products":[],"references":[{"url":"https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8","tags":[]},{"url":"https://github.com/Bubka/2FAuth/releases/tag/v8.0.0","tags":[]},{"url":"https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457","tags":[]},{"url":"https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457","tags":[]}],"exploitRefs":[{"url":"https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8","tags":[]},{"url":"https://github.com/Bubka/2FAuth/releases/tag/v8.0.0","tags":[]},{"url":"https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457","tags":[]},{"url":"https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457","tags":[]}],"hasPoc":true,"ai":{"summary":"A reverse proxy authentication bypass allows unauthenticated users to impersonate any existing user, including administrators, by forging a trusted identity header when AUTHENTICATION_GUARD=reverse-proxy-guard is enabled, leading to full compromise of 2FA secrets and administrative functions.","exploitability":"Exploitation is trivial for an attacker who can send direct HTTP requests to the application without going through a trusted reverse proxy; no authentication or user interaction is required.","blast_radius":"Successful exploitation grants full access to all stored 2FA secrets, account management features, and administrative controls, enabling credential theft, lateral movement, and complete system takeover.","remediation":"Upgrade to 2FAuth version 8.0.0 or later, which fixes the vulnerability by validating that requests originate from configured trusted proxies before accepting the identity header.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["auth-bypass","reverse-proxy","2fa","identity-theft","web-app"],"model":"garnet-coder","analyzedAt":"2026-11-07T09:54:44.241Z"}}