CVE-2026-27659

published 2026-03-25

CVE-2026-27659: Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the…

Priority P4 25 medium 4.6 CVSS 3.1

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

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request.. Mattermost Advisory ID: MMSA-2026-00578

Affected

13 ranges

Vendor	Product	Version range	Fixed in
github.com	mattermost_mattermost_server_v8	>= 10.11.0-rc1 < 10.11.11	10.11.11
github.com	mattermost_mattermost_server_v8	>= 11.2.0-rc1 < 11.2.3	11.2.3
github.com	mattermost_mattermost_server_v8	>= 11.3.0-rc1 < 11.3.2	11.3.2
github.com	mattermost_mattermost_server_v8	>= 11.4.0-rc1 < 11.4.1	11.4.1
github.com	mattermost_mattermost_server_v8	>= 8.0.0-20260105080200-d27a2195068d < 10.11.11	10.11.11
mattermost	mattermost	10.11.0 – 10.11.10	—
mattermost	mattermost	11.2.0 – 11.2.2	—
mattermost	mattermost	11.3.0 – 11.3.1	—
mattermost	mattermost	11.4.0 – 11.4.0	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.11	10.11.11
mattermost	mattermost_server	>= 11.2.0 < 11.2.3	11.2.3
mattermost	mattermost_server	>= 11.3.0 < 11.3.2	11.3.2
mattermost	mattermost_server	>= 11.4.0 < 11.4.1	11.4.1

Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.

CWE-352