CVE-2026-9820: Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the…

PriorityP417low3.8CVSS 3.1

AVNACLPRHUINSUCLILAN

EPSS

0.15%

4.9th percentile

Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671

Affected

4 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	10.11.0 – 10.11.19	—
mattermost	mattermost	11.7.0 – 11.7.2	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.20	10.11.20
mattermost	mattermost_server	>= 11.7.0 < 11.7.3	11.7.3

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