{
    "id": "CVE-2018-18955",
    "published": "2018-11-16 20:29:00",
    "last_modified": "2026-06-17 01:48:10",
    "cvss_score": "7.0",
    "cvss_severity": "HIGH",
    "cvss_version": "3.0",
    "cvss_vector": "CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
    "cwe": "CWE-863",
    "description": "In the Linux kernel 4.15.x through 4.19.x before 4.19.2, map_write() in kernel/user_namespace.c allows privilege escalation because it mishandles nested user namespaces with more than 5 UID or GID ranges. A user who has CAP_SYS_ADMIN in an affected user namespace can bypass access controls on resources outside the namespace, as demonstrated by reading /etc/shadow. This occurs because an ID transformation takes place properly for the namespaced-to-kernel direction but not for the kernel-to-namespaced direction.",
    "epss_score": "0.07611",
    "epss_percentile": "0.94382",
    "kev": 0,
    "kev_due": null,
    "has_exploit": 1,
    "updated_at": "2026-10-03 18:17:20",
    "priority": {
        "rank": 2,
        "label": "Patch early",
        "why": "A public exploit exists."
    },
    "products": [
        {
            "vendor": "canonical",
            "product": "ubuntu_linux"
        },
        {
            "vendor": "linux",
            "product": "linux_kernel"
        }
    ],
    "kev_detail": null,
    "exploits": [
        {
            "source": "exploit-db",
            "ref_id": "47165",
            "title": "Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (dbus Method)",
            "date": "2019-01-04",
            "url": "https://www.exploit-db.com/exploits/47165"
        },
        {
            "source": "exploit-db",
            "ref_id": "47167",
            "title": "Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (polkit Method)",
            "date": "2019-01-04",
            "url": "https://www.exploit-db.com/exploits/47167"
        },
        {
            "source": "exploit-db",
            "ref_id": "45915",
            "title": "Linux - Nested User Namespace idmap Limit Local Privilege Escalation (Metasploit)",
            "date": "2018-11-29",
            "url": "https://www.exploit-db.com/exploits/45915"
        },
        {
            "source": "exploit-db",
            "ref_id": "47164",
            "title": "Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (cron Method)",
            "date": "2018-11-21",
            "url": "https://www.exploit-db.com/exploits/47164"
        },
        {
            "source": "exploit-db",
            "ref_id": "47166",
            "title": "Linux Kernel 4.15.x < 4.19.2 - 'map_write() CAP_SYS_ADMIN' Local Privilege Escalation (ldpreload Method)",
            "date": "2018-11-21",
            "url": "https://www.exploit-db.com/exploits/47166"
        },
        {
            "source": "exploit-db",
            "ref_id": "45886",
            "title": "Linux - Broken uid/gid Mapping for Nested User Namespaces",
            "date": "2018-11-16",
            "url": "https://www.exploit-db.com/exploits/45886"
        }
    ],
    "refs_list": [
        "http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd",
        "http://www.securityfocus.com/bid/105941",
        "https://bugs.chromium.org/p/project-zero/issues/detail?id=1712",
        "https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19",
        "https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2",
        "https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd",
        "https://security.netapp.com/advisory/ntap-20190416-0003/",
        "https://support.f5.com/csp/article/K39103040",
        "https://usn.ubuntu.com/3832-1/",
        "https://usn.ubuntu.com/3833-1/",
        "https://usn.ubuntu.com/3835-1/",
        "https://usn.ubuntu.com/3836-1/",
        "https://usn.ubuntu.com/3836-2/",
        "https://www.exploit-db.com/exploits/45886/",
        "https://www.exploit-db.com/exploits/45915/",
        "http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd",
        "http://www.securityfocus.com/bid/105941",
        "https://bugs.chromium.org/p/project-zero/issues/detail?id=1712",
        "https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19",
        "https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2",
        "https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd",
        "https://security.netapp.com/advisory/ntap-20190416-0003/",
        "https://support.f5.com/csp/article/K39103040",
        "https://usn.ubuntu.com/3832-1/",
        "https://usn.ubuntu.com/3833-1/"
    ]
}