Improper file ownership validation in the Boards API allows unauthorised file access_CVE-2026-3473

{
    "lastseen": "",
    "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",
    "published": "2026-05-22T10:27:02.600Z",
    "modified": "2026-05-22T12:12:49.437Z",
    "type": "cve",
    "title": "Improper file ownership validation in the Boards API allows unauthorised file access",
    "source": "Mattermost",
    "references": "https://mattermost.com/security-updates",
    "id": "CVE-2026-3473",
    "bulletinFamily": "",
    "cwe": [
        "CWE-639"
    ],
    "cvelist": null,
    "sourceData": "Mattermost Mattermost 11.6.0\nMattermost Mattermost 11.5.0\nMattermost Mattermost 11.4.0\nMattermost Mattermost 10.11.0",
    "sourceHref": "",
    "cvss": {
        "score": 5.9,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N",
        "version": "3.1"
    },
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        "baseScore": 0,
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        "confidentialityImpact": "",
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        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
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    "product": "Mattermost",
    "version": "11.6.0",
    "vendor": "Mattermost",
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}