CVE-2026-2458: Mattermost allows a removed team member to enumerate all public channels within a private team

March 16, 2026 (updated March 17, 2026)

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate team membership when searching channels which allows a removed team member to enumerate all public channels within a private team via the channel search API endpoint. Mattermost Advisory ID: MMSA-2025-00568

References

github.com/advisories/GHSA-679f-wmrg-qf57
github.com/mattermost/mattermost
github.com/mattermost/mattermost/commit/a18b80ba4c324b74b3d47951c33957305af4a099
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-2458

Code Behaviors & Features

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