Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

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Fixes

Solution

Update Mattermost to versions 11.9.0, 10.11.21, 11.7.6 or higher.


Workaround

No workaround given by the vendor.

References
History

Mon, 17 Aug 2026 23:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 17 Aug 2026 22:30:00 +0000

Type Values Removed Values Added
Description Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682
Title Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite
Weaknesses CWE-459
References
Metrics cvssV3_1

{'score': 3.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-08-17T22:07:12.958Z

Reserved: 2026-05-27T10:58:39.051Z

Link: CVE-2026-9693

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-17T23:16:52.940

Modified: 2026-08-17T23:16:52.940

Link: CVE-2026-9693

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T23:30:04Z

Weaknesses