9p: fix access mode flags being ORed instead of replaced_CVE-2026-52906

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p: fix access mode flags being ORed instead of replaced\n\nSince commit 1f3e4142c0eb (\"9p: convert to the new mount API\"),\nv9fs_apply_options() applies parsed mount flags with |= onto flags\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\n\"access=user\", both bits end up set. Access mode checks compare\nagainst exact values, so having both bits set matches neither mode.\n\nThis causes v9fs_fid_lookup() to fall through to the default switch\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\nfor all fid lookups. Root is then unable to chown or perform other\nprivileged operations.\n\nFix by clearing the access mask before applying the user's choice.",
    "published": "2026-06-09T12:36:03.521Z",
    "modified": "2026-06-14T04:30:31.711Z",
    "type": "cve",
    "title": "9p: fix access mode flags being ORed instead of replaced",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058\nhttps://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9",
    "id": "CVE-2026-52906",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 1f3e4142c0eb178089ea0cbc97506a061470ad27\nLinux Linux 1f3e4142c0eb178089ea0cbc97506a061470ad27\nLinux Linux 6.19",
    "sourceHref": "",
    "cvss": {
        "score": 7.7,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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            "baseScore": 0,
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            "privilegesRequired": "",
            "userInteraction": "",
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            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "1f3e4142c0eb178089ea0cbc97506a061470ad27",
    "vendor": "Linux",
    "ai_description": "",
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    "ai_score": 0
}