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CVE-2026-8821: mattermost server from 10.11.0 (inclusive), before 10.11.23 (exclusive), from 11.7.0 (inclusive), before 11.7.8…
CVE-2026-8821. CVSS 3.1 base score 7.1 (HIGH, Vendor/CNA). EPSS 0.0029 (percentile 0.19679), scored 2026-10-06.
Affected technology
mattermost server · from 10.11.0 (inclusive), before 10.11.23 (exclusive)
mattermost
mattermost server · from 11.7.0 (inclusive), before 11.7.8 (exclusive)
mattermost
mattermost server · from 11.8.0 (inclusive), before 11.8.5 (exclusive)
mattermost
mattermost server · from 11.9.0 (inclusive), before 11.9.1 (exclusive)
mattermost
Mattermost · 11.9.0 through 11.9.0, 11.8.0 through 11.8.4, 11.7.0 through 11.7.7, 10.11.0 through 10.11.22
Mattermost
Description’s affected range: versions 11.9.x <= 11.9.0
Component: Not specified by the source
Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · Low privileges required · No user interaction required
What an attacker can do
An authenticated channel member to add an arbitrary user can a restricted channel via the run owner field. Vendor/CNA’s CVSS 3.1 assessment (base score 7.1/10) rates confidentiality impact as high; integrity impact as low; availability impact as none.
- CWE
- CWE-862
- CCR priority
- 28.5 /100 (P4)
- CVSS 3.1
- 7.1 /10 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N · Vendor/CNA
- EPSS
- 0.0029 · percentile 0.19679 · 2026-10-06
- KEV
- no
Provenance
- NVD CVE API 2.0 · Source record · observed 2026-10-07 15:46:54.698485+00:00 UTC
Stable permalink: https://cybercodered.org/item/cve-cve-2026-8821.html