CVE-2026-9820 Details
Description
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 share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671
A vulnerability exists in Mattermost versions 11.7.x prior to 11.7.2 and 10.11.x prior to 10.11.19. The issue arises because the application fails to properly sanitize team objects returned by the scheme teams endpoint. This flaw allows users with the User Manager role to obtain invite links for private teams. These links can then be used to join or share access to those teams via the scheme teams API endpoint.
Users can upgrade to Mattermost versions 11.9.0 or 11.8.0 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 13, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://mattermost.com/security-updates | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-862 | Missing Authorization | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mattermost mattermost server | >= 10.11.0, < 10.11.20 >= 11.7.0, < 11.7.3 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 13, 2026 | Initial Analysis | [email protected] |
| Jul 13, 2026 | CVE Modified | CISA-ADP |
| Jul 13, 2026 | New CVE Received | [email protected] |