Mattermost doesn't rate limit login requests, allowing DoS

GHSA-247x-7qw8-fp98 · CVE-2026-26233 · GO-2026-4916

Published Mar 25, 2026 · Modified Apr 6, 2026

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

ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-26233
PACKAGE https://github.com/mattermost/mattermost
WEB https://mattermost.com/security-updates

Ready to move

Start Securing

Start for Free Get Demo

Free, no credit card | First findings in minutes