---
cve: "CVE-2026-9816"
severity: "HIGH"
cvss: 8.3
epss: "25%"
vendor: "Mattermost"
kev: false
exploited: false
published: "2026-08-17 22:17:27"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-13T19:52:00+02:00"
---

# CVE-2026-9816

> 8.3 HIGH

## Beschreibung

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/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 | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- d6dbfe06f8abbe0d9d57cf47dc322042a826eb42 (Commit)
- 2045acd92c40353abfc5ffff8ae1e0dd9d2e6737 (Commit)

## Referenzen

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

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-9816) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_