CVE-2026-28735 MEDIUM

CVE-2026-28735: GitHub OAuth Scope Validation

Vendor Mattermost
Product Mattermost
Weakness CWE-863 · Incorrect authorization
Published May 22, 2026
Last update May 22, 2026
View on NVD All CVEs

CVSS base score

5.4/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality Low
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

May 22, 2026 CVE published
May 22, 2026 Record updated