Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access_CVE-2026-4274

{
    "lastseen": "",
    "description": "Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574",
    "published": "2026-03-26T10:43:24.611Z",
    "modified": "2026-03-26T13:58:41.567Z",
    "type": "cve",
    "title": "Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access",
    "source": "Mattermost",
    "references": "https://mattermost.com/security-updates",
    "id": "CVE-2026-4274",
    "bulletinFamily": "",
    "cwe": [
        "CWE-863"
    ],
    "cvelist": null,
    "sourceData": "Mattermost Mattermost 11.2.0\nMattermost Mattermost 10.11.0\nMattermost Mattermost 11.4.0\nMattermost Mattermost 11.3.0",
    "sourceHref": "",
    "cvss": {
        "score": 5.4,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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            "baseScore": 0,
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Mattermost",
    "version": "11.2.0",
    "vendor": "Mattermost",
    "ai_description": "",
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    "ai_score": 0
}