CVE-2026-91181: 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 sanitize Team objects returned by the data retention…

PriorityP339medium6.5CVSS 3.1

AVNACLPRHUINSUCHIHAN

EPSS

0.39%

31.5th percentile

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 sanitize Team objects returned by the data retention teams endpoint which allows an authenticated user holding only the read-only Data Retention Policy permission to obtain a private team's secret invite_id and email, and use it to join the team without authorization, via GET /api/v4/data_retention/policies/{policy_id}/teams.. Mattermost Advisory ID: MMSA-2026-00702

Affected

8 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	10.11.0 – 10.11.22	—
mattermost	mattermost	11.7.0 – 11.7.7	—
mattermost	mattermost	11.8.0 – 11.8.4	—
mattermost	mattermost	11.9.0 – 11.9.0	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.23	10.11.23
mattermost	mattermost_server	>= 11.7.0 < 11.7.8	11.7.8
mattermost	mattermost_server	>= 11.8.0 < 11.8.5	11.8.5
mattermost	mattermost_server	>= 11.9.0 < 11.9.1	11.9.1

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