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Vulnerable Software

Vulnerability Details CVE-2026-8821

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

Exploit prediction scoring system (EPSS) score

EPSS Score 0.003

EPSS Ranking 19.7%

CVSS Severity

CVSS v3 Score 7.1

References

https://mattermost.com/security-updates

Products affected by CVE-2026-8821

Mattermost » Mattermost Server » Version: 10.11.0

cpe:2.3:a:mattermost:mattermost_server:10.11.0
Mattermost » Mattermost Server » Version: 10.11.1

cpe:2.3:a:mattermost:mattermost_server:10.11.1
Mattermost » Mattermost Server » Version: 10.11.10

cpe:2.3:a:mattermost:mattermost_server:10.11.10
Mattermost » Mattermost Server » Version: 10.11.11

cpe:2.3:a:mattermost:mattermost_server:10.11.11
Mattermost » Mattermost Server » Version: 10.11.12

cpe:2.3:a:mattermost:mattermost_server:10.11.12
Mattermost » Mattermost Server » Version: 10.11.13

cpe:2.3:a:mattermost:mattermost_server:10.11.13
Mattermost » Mattermost Server » Version: 10.11.14

cpe:2.3:a:mattermost:mattermost_server:10.11.14
Mattermost » Mattermost Server » Version: 10.11.15

cpe:2.3:a:mattermost:mattermost_server:10.11.15
Mattermost » Mattermost Server » Version: 10.11.16

cpe:2.3:a:mattermost:mattermost_server:10.11.16
Mattermost » Mattermost Server » Version: 10.11.17

cpe:2.3:a:mattermost:mattermost_server:10.11.17
Mattermost » Mattermost Server » Version: 10.11.18

cpe:2.3:a:mattermost:mattermost_server:10.11.18
Mattermost » Mattermost Server » Version: 10.11.19

cpe:2.3:a:mattermost:mattermost_server:10.11.19
Mattermost » Mattermost Server » Version: 10.11.2

cpe:2.3:a:mattermost:mattermost_server:10.11.2
Mattermost » Mattermost Server » Version: 10.11.20

cpe:2.3:a:mattermost:mattermost_server:10.11.20
Mattermost » Mattermost Server » Version: 10.11.21

cpe:2.3:a:mattermost:mattermost_server:10.11.21
Mattermost » Mattermost Server » Version: 10.11.22

cpe:2.3:a:mattermost:mattermost_server:10.11.22
Mattermost » Mattermost Server » Version: 10.11.3

cpe:2.3:a:mattermost:mattermost_server:10.11.3
Mattermost » Mattermost Server » Version: 10.11.4

cpe:2.3:a:mattermost:mattermost_server:10.11.4
Mattermost » Mattermost Server » Version: 10.11.5

cpe:2.3:a:mattermost:mattermost_server:10.11.5
Mattermost » Mattermost Server » Version: 10.11.6

cpe:2.3:a:mattermost:mattermost_server:10.11.6
Mattermost » Mattermost Server » Version: 10.11.7

cpe:2.3:a:mattermost:mattermost_server:10.11.7
Mattermost » Mattermost Server » Version: 10.11.8

cpe:2.3:a:mattermost:mattermost_server:10.11.8
Mattermost » Mattermost Server » Version: 10.11.9

cpe:2.3:a:mattermost:mattermost_server:10.11.9
Mattermost » Mattermost Server » Version: 11.7.0

cpe:2.3:a:mattermost:mattermost_server:11.7.0
Mattermost » Mattermost Server » Version: 11.7.1

cpe:2.3:a:mattermost:mattermost_server:11.7.1
Mattermost » Mattermost Server » Version: 11.7.2

cpe:2.3:a:mattermost:mattermost_server:11.7.2
Mattermost » Mattermost Server » Version: 11.7.3

cpe:2.3:a:mattermost:mattermost_server:11.7.3
Mattermost » Mattermost Server » Version: 11.7.4

cpe:2.3:a:mattermost:mattermost_server:11.7.4
Mattermost » Mattermost Server » Version: 11.7.5

cpe:2.3:a:mattermost:mattermost_server:11.7.5
Mattermost » Mattermost Server » Version: 11.7.6

cpe:2.3:a:mattermost:mattermost_server:11.7.6
Mattermost » Mattermost Server » Version: 11.7.7

cpe:2.3:a:mattermost:mattermost_server:11.7.7
Mattermost » Mattermost Server » Version: 11.8.0

cpe:2.3:a:mattermost:mattermost_server:11.8.0
Mattermost » Mattermost Server » Version: 11.8.1

cpe:2.3:a:mattermost:mattermost_server:11.8.1
Mattermost » Mattermost Server » Version: 11.8.2

cpe:2.3:a:mattermost:mattermost_server:11.8.2
Mattermost » Mattermost Server » Version: 11.8.3

cpe:2.3:a:mattermost:mattermost_server:11.8.3
Mattermost » Mattermost Server » Version: 11.8.4

cpe:2.3:a:mattermost:mattermost_server:11.8.4

Vulnerabilities

Vulnerable Software

Vulnerability Details CVE-2026-8821

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