CVE-2026-12882

published 2026-09-14

CVE-2026-12882: 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 parse Markdown autolinks with unmatched trailing closing…

Priority P4 23 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 <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to parse Markdown autolinks with unmatched trailing closing parentheses in linear time, which allows an authenticated user with permission to create posts to cause excessive server CPU consumption and degrade availability for other users via specially crafted post or message attachment content. Mattermost Advisory ID: MMSA-2026-00703

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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CWE-407