What is CVE-2026-9820?

CVE-2026-9820 is a low-severity vulnerability in Mattermost, classified under Missing Authorization. CVSS score: 3.8/10. Published 2026-07-13.

How severe is CVE-2026-9820?

Low severity. CVSS v3 base score is 3.8 out of 10.

Auth bypass in Mattermost

CVE-2026-9820

Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or…

Vulnerability class: Broken Access Control

CVSS v3 metric

CVSS v3 base score 3.8 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N.

Affected products

Mattermost — versions 11.7.0, 10.11.0, 11.8.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-9820?: CVE-2026-9820 is a low-severity vulnerability in Mattermost, classified under Missing Authorization. CVSS score: 3.8/10. Published 2026-07-13.
How severe is CVE-2026-9820?: Low severity. CVSS v3 base score is 3.8 out of 10.