---
cve: "CVE-2026-63438"
severity: "CRITICAL"
cvss: 9.8
epss: "0.5%"
vendor: "Bubka"
kev: false
exploited: false
published: "2026-11-06 21:17:09"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-11-08T09:36:34+01:00"
---

# CVE-2026-63438

> 9.8 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **GitHub_M**
- State: PUBLISHED
- Stand: 2026-11-06 20:20:27
- CNA-CVSS: **9.8** (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Schwachstellen-Klasse

- **CWE-287** — Improper Authentication
  When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

## Angriffsmuster (CAPEC)

- [CAPEC-22 — Exploiting Trust in Client](https://capec.mitre.org/data/definitions/22.html) _(Severity: High)_
- [CAPEC-57 — Utilizing REST's Trust in the System Resource to Obtain Sensitive Data](https://capec.mitre.org/data/definitions/57.html) _(Severity: Very High)_
- [CAPEC-114 — Authentication Abuse](https://capec.mitre.org/data/definitions/114.html) _(Severity: Medium)_
- [CAPEC-115 — Authentication Bypass](https://capec.mitre.org/data/definitions/115.html) _(Severity: Medium)_
- [CAPEC-151 — Identity Spoofing](https://capec.mitre.org/data/definitions/151.html) _(Severity: Medium)_
- [CAPEC-194 — Fake the Source of Data](https://capec.mitre.org/data/definitions/194.html) _(Severity: Medium)_
- [CAPEC-593 — Session Hijacking](https://capec.mitre.org/data/definitions/593.html) _(Severity: Very High)_
- [CAPEC-633 — Token Impersonation](https://capec.mitre.org/data/definitions/633.html) _(Severity: Medium)_

## ATT&CK-Techniken

- [T1040 — Network Sniffing](https://attack.mitre.org/techniques/T1040/)
- [T1548 — Abuse Elevation Control Mechanism](https://attack.mitre.org/techniques/T1548/)
- [T1185 — Browser Session Hijacking](https://attack.mitre.org/techniques/T1185/)
- [T1550.001 — Use Alternate Authentication Material:Application Access Tok](https://attack.mitre.org/techniques/T1550/001/)
- [T1563 — Remote Service Session Hijacking](https://attack.mitre.org/techniques/T1563/)
- [T1134 — Access Token Manipulation](https://attack.mitre.org/techniques/T1134/)

## Patch verfügbar (OSV)

- 4efbf2cf69eef65e8e3fa7a62ac53fc517e5d851 (Commit)
- 43873cbfba445926c7008b4291eeee67752af9e8 (Commit)

## Referenzen

- <https://github.com/Bubka/2FAuth/security/advisories/GHSA-r9xx-45m8-mw24>
- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-63438/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_