CVE-2026-26233

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.4.0 and earlier Mattermost versions 11.3.1 and earlier Mattermost versions 11.2.3 and earlier Mattermost versions 10.11.11 and earlier

Description The software does not adequately limit the rate of login requests. This allows unauthenticated remote attackers to cause a denial of service, potentially leading to server crashes and restarts, through an HTTP/2 single packet attack involving a large number of parallel login requests (100+).

Recommendations Update Mattermost to a version later than 11.4.0. Update Mattermost to a version later than 11.3.1. Update Mattermost to a version later than 11.2.3. Update Mattermost to a version later than 10.11.11.