# CVE-2026-63438: 2FAuth: Reverse Proxy Guard Auto-Creates Users With Admin Promotion From Unauthenticated Header Value

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Bubka / 2FAuth: < 8.0.0 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-287

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/Bubka/2FAuth/security/advisories/GHSA-r9xx-45m8-mw24 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/Bubka/2FAuth/commit/8a4c395cac97f8b70b4a822639a6ad8a816f927c (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/Bubka/2FAuth/commit/d9e58ac4a63fbd8a073e423567881c81a87915de (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/Bubka/2FAuth/releases/tag/v8.0.0 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-63438; retrieved 2026-11-06; source updated 2026-11-06

Revision: 6081d76b2a51f91fbaa0c486fdb277d8a17f60dbd1434e0a571e370b97587799

Canonical: https://y2.dev/cve/CVE-2026-63438

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