CVE-2026-8821CWE-862broken-access-control

CVE-2026-8821

High · published September 14, 2026

CVSS v3.1
7.1
EPSS
0%
Percentile
20.4
In the wild
Unconfirmed
What it is

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel member-management permission during playbook run creation, allowing an authenticated channel member to add an arbitrary user to a restricted channel via the run owner field.. Mattermost Advisory ID: MMSA-2026-00677

The record
Technical detail
CVSS v3.1
7.1 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00290 · 20.4th percentile
Weakness
CWE-862 · Missing Authorization
Published
2026-09-14T15:17Z
Affected products (4)
ProductVersionsFixed in
mattermost/mattermost_server≥ 10.11.0, < 10.11.2310.11.23
mattermost/mattermost_server≥ 11.7.0, < 11.7.811.7.8
mattermost/mattermost_server≥ 11.8.0, < 11.8.511.8.5
mattermost/mattermost_server≥ 11.9.0, < 11.9.111.9.1
References (1)
https://mattermost.com/security-updates · [email protected]
EPSS history
Timeline
  • 17 SEP 03:33Z
    EPSS moved — → 0%
    epss
  • 14 SEP 10:42Z
    Playbooks run owner channel membership permission bypass
    cvelistv5