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CVE-2026-18551: Mattermost 11.10.0 through 11.10.0, 11.7.0 through 11.7.9, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5
CVE-2026-18551. CVSS 3.1 base score 6.5 (MEDIUM, Vendor/CNA).
Affected technology
Mattermost · 11.10.0 through 11.10.0, 11.7.0 through 11.7.9, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5
Mattermost
Description’s affected range: versions 11.10.x <= 11.10.0
Component: Not specified by the source
Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · High privileges required · No user interaction required
What an attacker can do
An authenticated attacker can escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint. Vendor/CNA’s CVSS 3.1 assessment (base score 6.5/10) rates confidentiality and integrity impact as high; availability impact as none.
- CWE
- CWE-863
- CCR priority
- 26.0 /100 (P4)
- CVSS 3.1
- 6.5 /10 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N · Vendor/CNA
- KEV
- no
Provenance
- NVD CVE API 2.0 · Source record · observed 2026-10-16 07:51:53.906443+00:00 UTC
Stable permalink: https://cybercodered.org/item/cve-cve-2026-18551.html