CVE-2026-63438

Summary

The flaw allows unauthenticated attackers to create or impersonate administrator accounts in 2FAuth by exploiting improper validation of reverse proxy authentication headers, leading to full system compromise including access to 2FA secrets.

Exploitability

Exploitation requires no authentication and can be performed remotely against a fresh or existing instance where AUTHENTICATION_GUARD=reverse-proxy-guard is enabled and the server does not enforce trusted proxy checks.

Blast radius

Successful exploitation grants full administrative control, enabling theft of 2FA secrets, account takeover, and potential lateral movement within the protected infrastructure.

Detection

Look for unexpected creation of new user accounts with administrative privileges in application logs, especially when accompanied by requests containing REMOTE_USER and mail headers from untrusted IP ranges or without prior successful authentication events.

Prioritized remediation

Upgrade to 2FAuth version 8.0.0 or later, which fixes the vulnerability by properly validating reverse proxy authentication headers.

Analysis generated locally by garnet-coder (no data left the box). AI-assisted — verify against primary sources before acting.