CVE-2026-26233

published 2026-03-25

CVE-2026-26233: Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated…

medium 6.5 CVSS 3.1

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

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566

Affected

16 ranges

Vendor	Product	Version range	Fixed in
github.com	mattermost_mattermost-server	>= 10.11.0-rc1 < 10.11.12	10.11.12
github.com	mattermost_mattermost-server	>= 10.11.0-rc1+incompatible < 10.11.12+incompatible	10.11.12+incompatible
github.com	mattermost_mattermost-server	>= 11.2.0-rc1 < 11.2.4	11.2.4
github.com	mattermost_mattermost-server	>= 11.2.0-rc1+incompatible < 11.2.4+incompatible	11.2.4+incompatible
github.com	mattermost_mattermost-server	>= 11.3.0-rc1 < 11.3.2	11.3.2
github.com	mattermost_mattermost-server	>= 11.3.0-rc1+incompatible < 11.3.2+incompatible	11.3.2+incompatible
github.com	mattermost_mattermost-server	>= 11.4.0-rc1 < 11.4.1	11.4.1
github.com	mattermost_mattermost-server	>= 11.4.0-rc1+incompatible < 11.4.1+incompatible	11.4.1+incompatible
mattermost	mattermost	10.11.0 – 10.11.11	—
mattermost	mattermost	11.2.0 – 11.2.3	—
mattermost	mattermost	11.3.0 – 11.3.1	—
mattermost	mattermost	11.4.0 – 11.4.0	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.12	10.11.12
mattermost	mattermost_server	>= 11.2.0 < 11.2.4	11.2.4
mattermost	mattermost_server	>= 11.3.0 < 11.3.2	11.3.2
mattermost	mattermost_server	>= 11.4.0 < 11.4.1	11.4.1

CWE-400