{"id":"CVE-2026-4265","state":"PUBLISHED","title":"Guest user can upload files without permission across teams","description":"Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553","publishedAt":"2026-03-16T12:07:14.659Z","updatedAt":"2026-03-16T13:49:55.080Z","severity":{"score":4.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","source":"Mattermost"},"assigner":"Mattermost","products":["Mattermost Mattermost"],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.3.0","status":"affected","lessThanOrEqual":"11.3.0","versionType":"semver"},{"version":"11.2.0","status":"affected","lessThanOrEqual":"11.2.2","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.10","versionType":"semver"},{"version":"11.4.0","status":"unaffected"},{"version":"11.3.1","status":"unaffected"},{"version":"11.2.3","status":"unaffected"},{"version":"10.11.11","status":"unaffected"}]}],"references":["https://mattermost.com/security-updates"],"weaknesses":["CWE-863"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/4xxx/CVE-2026-4265.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-4265","state":"PUBLISHED","datePublished":"2026-03-16T12:07:14.659Z","dateUpdated":"2026-03-16T13:49:55.080Z","assignerShortName":"Mattermost","assignerOrgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateReserved":"2026-03-16T12:05:32.172Z"},"containers":{"cna":{"title":"Guest user can upload files without permission across teams","descriptions":[{"lang":"en","value":"Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553"}],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.3.0","status":"affected","lessThanOrEqual":"11.3.0","versionType":"semver"},{"version":"11.2.0","status":"affected","lessThanOrEqual":"11.2.2","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.10","versionType":"semver"},{"version":"11.4.0","status":"unaffected"},{"version":"11.3.1","status":"unaffected"},{"version":"11.2.3","status":"unaffected"},{"version":"10.11.11","status":"unaffected"}]}],"references":[{"url":"https://mattermost.com/security-updates","name":"MMSA-2025-00553","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"NONE","version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","baseSeverity":"MEDIUM","baseScore":4.3},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-863","lang":"en","type":"CWE","description":"CWE-863: Incorrect Authorization"}]}],"providerMetadata":{"shortName":"Mattermost","orgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateUpdated":"2026-03-16T12:07:14.659Z"},"credits":[{"lang":"en","type":"finder","value":"0x7oda7123"}],"solutions":[{"value":"Update Mattermost to versions 11.4.0, 11.3.1, 11.2.3, 10.11.11 or higher.","lang":"en"}],"source":{"advisory":"MMSA-2025-00553","defect":["https://mattermost.atlassian.net/browse/MM-66478"],"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-4265","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-03-16T13:41:40.647671Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-16T13:49:55.080Z"}}]}}}