CVE-2026-26233 MEDIUM

CVE-2026-26233: Denial of Service via HTTP/2 single packet attack on login endpoint

Vendor Mattermost
Product Mattermost
Weakness CWE-400
Published March 25, 2026
Last update March 27, 2026
View on NVD All CVEs

CVSS base score

4.3/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

March 25, 2026 CVE published
March 27, 2026 Record updated