---
cve: "CVE-2025-12421"
severity: "CRITICAL"
cvss: 9.9
epss: "35%"
vendor: "Mattermost"
kev: false
exploited: false
published: "2025-11-27 18:15:46"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-09T13:29:59+02:00"
---

# CVE-2025-12421

> 9.9 CRITICAL

## Beschreibung

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).

## CVSS-Vektor

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

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

## Patch verfügbar (OSV)

- 288281e8cbf15260ad074b883a263b796cdb3e28 (Commit)
- 46b5c436bb3093cc1da3fa2455f93d4c52389eee (Commit)

## Referenzen

- <https://mattermost.com/security-updates>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2025-12421) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_