EUVD-2026-31465
GHSA-r5vf-grcx-5vqp
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Lifecycle Timeline
1DescriptionNVD
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
AnalysisAI
OAuth scope validation bypass in Mattermost's GitHub integration allows authenticated users to escalate repository access beyond what was originally authorized. By manipulating the scope parameter in the GitHub OAuth authorization URL before the callback is processed, a low-privileged Mattermost user can obtain a GitHub token with broader permissions - including access to private repositories - than the application intended to grant. …
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