Missing request origin validation on burn-on-read reveal endpoint_CVE-2026-6339

{
    "lastseen": "",
    "description": "Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost Advisory ID: MMSA-2026-00636",
    "published": "2026-05-18T08:05:30.925Z",
    "modified": "2026-05-18T08:05:30.925Z",
    "type": "cve",
    "title": "Missing request origin validation on burn-on-read reveal endpoint",
    "source": "Mattermost",
    "references": "https://mattermost.com/security-updates",
    "id": "CVE-2026-6339",
    "bulletinFamily": "",
    "cwe": [
        "CWE-346"
    ],
    "cvelist": null,
    "sourceData": "Mattermost Mattermost 11.5.0\nMattermost Mattermost 11.4.0",
    "sourceHref": "",
    "cvss": {
        "score": 4.3,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
        "version": "3.1"
    },
    "cvss2": [],
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        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Mattermost",
    "version": "11.5.0",
    "vendor": "Mattermost",
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    "ai_score": 0
}