Mattermost up to 10.11.22/11.7.7/11.8.4/11.9.0 Playbook Run permission

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.22/11.7.7/11.8.4/11.9.0. It has been rated as critical. This affects an unknown part of the component Playbook Run. Performing a manipulation results in permission. This vulnerability is known as CVE-2026-8821. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical has been found in Mattermost up to 10.11.22/11.7.7/11.8.4/11.9.0. This affects an unknown function of the component Playbook Run. The manipulation with an unknown input leads to a permission vulnerability. CWE is classifying the issue as CWE-275. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE 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

It is possible to read the advisory at mattermost.com. This vulnerability is uniquely identified as CVE-2026-8821 since 05/18/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1222 according to MITRE ATT&CK.

Upgrading to version 10.11.23, 11.7.8, 11.8.5, 11.9.1 or 11.10.0 eliminates this vulnerability.

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Productinfo

Type

• Groupware Software

Name

• Mattermost

Version

• 10.11.0
• 10.11.1
• 10.11.2
• 10.11.3
• 10.11.4
• 10.11.5
• 10.11.6
• 10.11.7
• 10.11.8
• 10.11.9
• 10.11.10
• 10.11.11
• 10.11.12
• 10.11.13
• 10.11.14
• 10.11.15
• 10.11.16
• 10.11.17
• 10.11.18
• 10.11.19
• 10.11.20
• 10.11.21
• 10.11.22
• 11.0
• 11.1
• 11.2
• 11.3
• 11.4
• 11.5
• 11.6
• 11.7
• 11.7.0
• 11.7.1
• 11.7.2
• 11.7.3
• 11.7.4
• 11.7.5
• 11.7.6
• 11.7.7
• 11.8
• 11.8.0
• 11.8.1
• 11.8.2
• 11.8.3
• 11.8.4
• 11.9.0

License

• open-source

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

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