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GHSA-r5vf-grcx-5vqp

Mattermost allows authenticated users to gain access to private repositories

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-28735

Packages

EcosystemPackageAffectedFixed in
Go github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1 11.6.1
Go github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.4 11.5.4
Go github.com/mattermost/mattermost-server >= 11.4.0, < 11.4.5 11.4.5
Go github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.15 10.11.15
Go github.com/mattermost/mattermost-plugin-github < 1.0.1-0.20260318132218-6e6b740c4852 1.0.1-0.20260318132218-6e6b740c4852

Details

As written in the advisory (Markdown source, shown as plain text).

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

References

External links from the advisory. They lead to third-party sites.