{"id":"CVE-2026-6961","aliases":["GHSA-8qq9-cqj8-82w4"],"title":"Mattermost doesn't sanitize FileInfo.Name received from federated peers during shared channel file sync","summary":"Mattermost doesn't sanitize FileInfo.Name received from federated peers during shared channel file sync","severity":"high","cvss":7.6,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/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, < 8.0.0-20260423180926-c021eeaff8f0"],"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 8.0.0-20260423180926-c021eeaff8f0"],"published":"2026-06-12","updated":"2026-08-25","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-8qq9-cqj8-82w4","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6961"},{"url":"https://github.com/mattermost/mattermost/pull/36255"},{"url":"https://github.com/mattermost/mattermost/pull/36253"},{"url":"https://github.com/mattermost/mattermost/pull/36252"},{"url":"https://github.com/mattermost/mattermost/pull/36251"},{"url":"https://github.com/mattermost/mattermost/pull/36223"},{"url":"https://github.com/mattermost/mattermost/commit/c896a63dc44c2f9c081a0a15bfddc4e6eb50e753"},{"url":"https://github.com/mattermost/mattermost/commit/c021eeaff8f003034ab40f82c552cc26a710a8fd"},{"url":"https://github.com/mattermost/mattermost/commit/a9f3868e1eee9ec61855cd7277f39937385efffd"},{"url":"https://github.com/mattermost/mattermost/commit/a0056ed68d95f64d7c4586985e7b7f16b96b3bec"},{"url":"https://github.com/mattermost/mattermost/commit/61d68d2d6ee81a5919597d91c736c502d7156859"},{"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"},{"url":"https://github.com/mattermost/mattermost"}],"tags":["osv","go"],"epss":0.00305,"epssPercentile":0.23431,"ingestedAt":"2026-08-25T19:26:22.992Z","slug":"CVE-2026-6961","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 sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations within the target server's filestore via path traversal sequences in the filename field. Mattermost Advisory ID: MMSA-2026-00661\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, < 8.0.0-20260423180926-c021eeaff8f0`\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 8.0.0-20260423180926-c021eeaff8f0`","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":41.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}