CVE-2026-63438 · Package
NO FIX YET · SEE WHAT TO DO
2FAuth, a web app that stores two-factor authentication accounts and generates their codes, trusts authentication headers from clients that did not come through the trusted reverse proxy when the reverse-proxy guard is enabled. An unauthenticated remote attacker can create an administrator account on a fresh instance, or take over and redirect the email of an existing account, which exposes 2FA secrets and admin functions.
first public Jul 1, 2026 · 1 source
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Only instances that set AUTHENTICATION_GUARD to reverse-proxy-guard are exposed. The flaw needs a client that can reach the application without passing through the trusted proxy, so an instance that only accepts traffic through the proxy is harder to reach. Self-hosted 2FAuth instances on a fresh install are the most at risk because the first account created becomes administrator.
Not affected if default-config, managed-hosting, proxy-only-access
Who cares 2fauth, php, reverse-proxy, self-hosted
AUTHENTICATION_GUARD is set to reverse-proxy-guard in the 2FAuth environment configuration.8.0.0 are affected.8.0.0 or later.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 accepts authentication headers from a client that did not pass through a trusted proxy, RemoteUserProvider::retrieveById() creates an account for an unknown REMOTE_USER, promotes the first created account to administrator, and synchronizes the account email from the configured mail header. An unauthenticated remote client can therefore create an administrator on a fresh instance or impersonate and redirect email for a known account, exposing 2FA secrets and administrative functions. This issue is fixed in version 8.0.0.
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