CVE-2026-26233

MEDIUM

Denial of Service via HTTP/2 single packet attack on login endpoint

Title source: cna

Description

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

References (1)

[Vendor Advisory] https://mattermost.com/security-updates

Scores

CVSS v3 4.3

EPSS 0.0010

EPSS Percentile 28.2%

Attack Vector NETWORK

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

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-400

Status published

Products (11)

Mattermost/Mattermost 10.11.0 - 10.11.11

Mattermost/Mattermost 10.11.12

Mattermost/Mattermost 11.2.0 - 11.2.3

Mattermost/Mattermost 11.2.4

Mattermost/Mattermost 11.3.0 - 11.3.1

Mattermost/Mattermost 11.3.2

Mattermost/Mattermost 11.4.0

Mattermost/Mattermost 11.4.1

Mattermost/Mattermost 11.5.0

mattermost/mattermost-server 11.4.0-rc1 - 11.4.1Go

... and 1 more

Published Mar 25, 2026

Tracked Since Mar 25, 2026