CVE-2026-28735

GitHub OAuth Scope Validation

State: Published
Severity: 5.4 Medium
Published: May 22, 2026
Updated: May 22, 2026
Reserved: Mar 10, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	5.4 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N	Mattermost

Weaknesses

CWE-863 Incorrect Authorization

Affected Products

Product	Versions
MattermostMattermost	11.6.0 through 11.6.0Affected 11.5.0 through 11.5.3Affected 11.4.0 through 11.4.4Affected 10.11.0 through 10.11.14Affected 11.7.0Not affected 11.6.1Not affected 11.5.4Not affected 11.4.5Not affected 10.11.15Not affected

References

MMSA-2026-00628vendor-advisory

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