CVE-2026-28735 Details
Description
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 the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628
A vulnerability exists in Mattermost versions 11.6.0, 11.5.3, 11.4.4, and 10.11.14, where the application fails to properly validate the OAuth token scope during the callback process. This flaw enables an authenticated Mattermost user to access private repositories by altering the scope parameter in the GitHub authorization URL.
Users can upgrade to Mattermost versions 11.8.0 or 11.7.18 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 May 22, 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-863 | Incorrect Authorization | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mattermost mattermost server | >= 10.11.0, < 10.11.15 >= 11.4.0, < 11.4.5 >= 11.5.0, < 11.5.4 >= 11.6.0, < 11.6.1 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 22, 2026 | Initial Analysis | [email protected] |
| May 22, 2026 | New CVE Received | [email protected] |