{"id":"CVE-2026-6739","aliases":["GHSA-m2w9-h2mm-79qr"],"title":"Mattermost doesn't require system-level permission when patching protected default system roles","summary":"Mattermost doesn't require system-level permission when patching protected default system roles","severity":"medium","cvss":6.7,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L","vendor":"mattermost","product":"github.com/mattermost/mattermost-server","ecosystem":"go","affected":["github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1","github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5","github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17","github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260501142004-99b73d4c4acf"],"patched":["github.com/mattermost/mattermost-server 11.6.1","github.com/mattermost/mattermost-server 11.5.5","github.com/mattermost/mattermost-server 10.11.17","github.com/mattermost/mattermost/server/v8 8.0.0-20260501142004-99b73d4c4acf"],"published":"2026-06-12","updated":"2026-08-24","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-m2w9-h2mm-79qr","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6739"},{"url":"https://github.com/mattermost/mattermost/pull/36197"},{"url":"https://github.com/mattermost/mattermost/pull/36377"},{"url":"https://github.com/mattermost/mattermost/pull/36379"},{"url":"https://github.com/mattermost/mattermost/pull/36380"},{"url":"https://github.com/mattermost/mattermost/pull/36382"},{"url":"https://github.com/mattermost/mattermost/commit/2c89c2f6768fbe4dfd57a21ca38c0aecead8d4a8"},{"url":"https://github.com/mattermost/mattermost/commit/5e159647b16e571b327ac6882f32eae42971f540"},{"url":"https://github.com/mattermost/mattermost/commit/8000e5933526f4fd66b92131db3a1b1f4520dbae"},{"url":"https://github.com/mattermost/mattermost/commit/f0a390b96e4c730daedbaf5190684776730218c7"},{"url":"https://github.com/mattermost/mattermost"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v10.11.16"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.5.5"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.6.2"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.7.0"},{"url":"https://mattermost.com/security-updates"}],"tags":["osv","go"],"epss":0.00257,"epssPercentile":0.17673,"ingestedAt":"2026-08-25T19:26:23.155Z","slug":"CVE-2026-6739","body":"## Overview\n\nMattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require system-level permission when patching protected default system roles, which allows authenticated users with delegated user-management permissions to escalate privileges by altering built-in role permissions via the role patch API. Mattermost Advisory ID: MMSA-2026-00656\n\n## Affected packages\n\n- `github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1`\n- `github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5`\n- `github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17`\n- `github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260501142004-99b73d4c4acf`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/mattermost/mattermost-server 11.6.1`\n- `github.com/mattermost/mattermost-server 11.5.5`\n- `github.com/mattermost/mattermost-server 10.11.17`\n- `github.com/mattermost/mattermost/server/v8 8.0.0-20260501142004-99b73d4c4acf`","depth":"sunlit","depthScore":37,"depthScoreParts":{"impact":36.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}