Is CVE-2026-12882 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-12882?

CVE-2026-12882 has a CVSS v3 severity of MEDIUM (4.3).

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CVE-2026-12882

Description

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