What is CVE-2026-9693?

CVE-2026-9693 is a low-severity vulnerability in Mattermost, classified under Incomplete Cleanup. CVSS score: 3.5/10. Published 2026-08-17.

How severe is CVE-2026-9693?

Low severity. CVSS v3 base score is 3.5 out of 10.

Vulnerability in Mattermost

CVE-2026-9693

Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

CVSS v3 metric

CVSS v3 base score 3.5 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N.

Affected products

Mattermost — versions 10.11.0, 11.7.0, 11.9.0

Weakness classification (CWE)

CWE-459 — Incomplete Cleanup

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-9693?: CVE-2026-9693 is a low-severity vulnerability in Mattermost, classified under Incomplete Cleanup. CVSS score: 3.5/10. Published 2026-08-17.
How severe is CVE-2026-9693?: Low severity. CVSS v3 base score is 3.5 out of 10.