CVE-2026-3473

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620

Score

CVSS 3.1 7.1 High

Status

Analyzed - responsibledisclosure@mattermost.com

Published

2026-05-22

Last modified

2026-05-22

Weaknesses

CWE-639

Affected products

• Mattermost (Mattermost)
• Mattermost Server (Mattermost)

References

• https://mattermost.com/security-updates