{"id":"CVE-2026-3473","state":"PUBLISHED","title":"Improper file ownership validation in the Boards API allows unauthorised file access","description":"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 file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620","publishedAt":"2026-05-22T10:27:02.600Z","updatedAt":"2026-05-22T12:12:49.437Z","severity":{"score":5.9,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N","source":"Mattermost"},"assigner":"Mattermost","products":["Mattermost Mattermost"],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.6.0","status":"affected","lessThanOrEqual":"11.6.0","versionType":"semver"},{"version":"11.5.0","status":"affected","lessThanOrEqual":"11.5.3","versionType":"semver"},{"version":"11.4.0","status":"affected","lessThanOrEqual":"11.4.4","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.14","versionType":"semver"},{"version":"11.7.0","status":"unaffected"},{"version":"11.6.1","status":"unaffected"},{"version":"11.5.4","status":"unaffected"},{"version":"11.4.5","status":"unaffected"},{"version":"10.11.15","status":"unaffected"}]}],"references":["https://mattermost.com/security-updates"],"weaknesses":["CWE-639"],"ingestedAt":"2026-10-29T20:11:50.837Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/3xxx/CVE-2026-3473.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-3473","state":"PUBLISHED","datePublished":"2026-05-22T10:27:02.600Z","dateUpdated":"2026-05-22T12:12:49.437Z","assignerShortName":"Mattermost","assignerOrgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateReserved":"2026-03-03T12:57:13.379Z"},"containers":{"cna":{"title":"Improper file ownership validation in the Boards API allows unauthorised file access","descriptions":[{"lang":"en","value":"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 file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620"}],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.6.0","status":"affected","lessThanOrEqual":"11.6.0","versionType":"semver"},{"version":"11.5.0","status":"affected","lessThanOrEqual":"11.5.3","versionType":"semver"},{"version":"11.4.0","status":"affected","lessThanOrEqual":"11.4.4","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.14","versionType":"semver"},{"version":"11.7.0","status":"unaffected"},{"version":"11.6.1","status":"unaffected"},{"version":"11.5.4","status":"unaffected"},{"version":"11.4.5","status":"unaffected"},{"version":"10.11.15","status":"unaffected"}]}],"references":[{"url":"https://mattermost.com/security-updates","name":"MMSA-2026-00620","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"LOW","availabilityImpact":"NONE","version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N","baseSeverity":"MEDIUM","baseScore":5.9},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-639","lang":"en","type":"CWE","description":"CWE-639: Authorization Bypass Through User-Controlled Key"}]}],"providerMetadata":{"shortName":"Mattermost","orgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateUpdated":"2026-05-22T10:27:02.600Z"},"credits":[{"lang":"en","type":"finder","value":"eahmed"}],"solutions":[{"value":"Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.","lang":"en"}],"source":{"advisory":"MMSA-2026-00620","defect":["https://mattermost.atlassian.net/browse/MM-67759"],"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-22T12:12:41.198607Z","id":"CVE-2026-3473","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-22T12:12:49.437Z"}}]}}}