Auth bypass in Bubka 2fauth
CVE-2026-63438
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.
Vulnerability class: Broken Authentication
Published .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Bubka 2fauth — versions < 8.0.0
Weakness classification (CWE)
References
- https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8
- https://github.com/Bubka/2FAuth/commit/8a4c395cac97f8b70b4a822639a6ad8a816f927c
- https://github.com/Bubka/2FAuth/commit/d9e58ac4a63fbd8a073e423567881c81a87915de
- https://github.com/Bubka/2FAuth/releases/tag/v8.0.0
- https://github.com/Bubka/2FAuth/security/advisories/GHSA-r9xx-45m8-mw24
Frequently asked questions
- What is CVE-2026-63438?
- CVE-2026-63438 is a critical-severity vulnerability in Bubka 2fauth, classified under Improper Authentication. CVSS score: 9.8/10. Published 2026-11-06.
- How severe is CVE-2026-63438?
- Critical severity. CVSS v3 base score is 9.8 out of 10.