CVE-2026-95666

published 2026-09-22

CVE-2026-95666: Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the…

Priority P4 24 medium 4.3 CVSS 3.1

AV N AC L PR L UI N S U C N I N A L

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771

Affected

8 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	11.10.0 – 11.10.1	—
mattermost	mattermost	11.7.0 – 11.7.10	—
mattermost	mattermost	11.8.0 – 11.8.5	—
mattermost	mattermost	11.9.0 – 11.9.1	—
mattermost	mattermost_server	>= 11.10.0 < 11.10.2	11.10.2
mattermost	mattermost_server	>= 11.7.0 < 11.7.11	11.7.11
mattermost	mattermost_server	>= 11.8.0 < 11.8.6	11.8.6
mattermost	mattermost_server	>= 11.9.0 < 11.9.2	11.9.2

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CWE-770