CVE-2026-9693

Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

State: Published
Severity: 3.5 Low
Published: Aug 17, 2026
Updated: Aug 18, 2026
Reserved: May 27, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	3.5 Low	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N	Mattermost

Weaknesses

CWE-459 Incomplete Cleanup

Affected Products

Product	Versions
MattermostMattermost	10.11.0 through 10.11.20Affected 11.7.0 through 11.7.5Affected 11.9.0Not affected 10.11.21Not affected 11.7.6Not affected

References

MMSA-2026-00682vendor-advisory

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