{
    "CVE_data_meta": {
        "AKA": "",
        "ASSIGNER": "security@ubuntu.com",
        "DATE_PUBLIC": "2020-10-13T16:00:00.000Z",
        "ID": "CVE-2020-16120",
        "STATE": "PUBLIC",
        "TITLE": "Unprivileged overlay + shiftfs read access"
    },
    "affects": {
        "vendor": {
            "vendor_data": [
                {
                    "product": {
                        "product_data": [
                            {
                                "product_name": "Linux kernel",
                                "version": {
                                    "version_data": [
                                        {
                                            "platform": "",
                                            "version_affected": "<",
                                            "version_name": "5.11-stable",
                                            "version_value": "5.11.0"
                                        }
                                    ]
                                }
                            }
                        ]
                    },
                    "vendor_name": "Linux kernel"
                }
            ]
        }
    },
    "configuration": [],
    "credit": [
        {
            "lang": "eng",
            "value": "Giuseppe Scrivano"
        }
    ],
    "data_format": "MITRE",
    "data_type": "CVE",
    "data_version": "4.0",
    "description": {
        "description_data": [
            {
                "lang": "eng",
                "value": "Overlayfs did not properly perform permission checking when copying up files in an overlayfs and could be exploited from within a user namespace, if, for example, unprivileged user namespaces were allowed. It was possible to have a file not readable by an unprivileged user to be copied to a mountpoint controlled by the user, like a removable device. This was introduced in kernel version 4.19 by commit d1d04ef (\"ovl: stack file ops\"). This was fixed in kernel version 5.8 by commits 56230d9 (\"ovl: verify permissions in ovl_path_open()\"), 48bd024 (\"ovl: switch to mounter creds in readdir\") and 05acefb (\"ovl: check permission to open real file\"). Additionally, commits 130fdbc (\"ovl: pass correct flags for opening real directory\") and 292f902 (\"ovl: call secutiry hook in ovl_real_ioctl()\") in kernel 5.8 might also be desired or necessary. These additional commits introduced a regression in overlay mounts within user namespaces which prevented access to files with ownership outside of the user namespace. This regression was mitigated by subsequent commit b6650da (\"ovl: do not fail because of O_NOATIMEi\") in kernel 5.11."
            }
        ]
    },
    "exploit": [],
    "generator": {
        "engine": "Vulnogram 0.0.9"
    },
    "impact": {
        "cvss": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 5.1,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
            "version": "3.1"
        }
    },
    "problemtype": {
        "problemtype_data": [
            {
                "description": [
                    {
                        "lang": "eng",
                        "value": "CWE-266 Incorrect Privilege Assignment"
                    }
                ]
            }
        ]
    },
    "references": {
        "reference_data": [
            {
                "name": "https://ubuntu.com/USN-4576-1",
                "refsource": "UBUNTU",
                "url": "https://ubuntu.com/USN-4576-1"
            },
            {
                "name": "https://ubuntu.com/USN-4577-1",
                "refsource": "UBUNTU",
                "url": "https://ubuntu.com/USN-4577-1"
            },
            {
                "name": "https://ubuntu.com/USN-4578-1",
                "refsource": "UBUNTU",
                "url": "https://ubuntu.com/USN-4578-1"
            },
            {
                "name": "https://www.openwall.com/lists/oss-security/2020/10/14/2",
                "refsource": "CONFIRM",
                "url": "https://www.openwall.com/lists/oss-security/2020/10/14/2"
            },
            {
                "name": "https://launchpad.net/bugs/1894980",
                "refsource": "UBUNTU",
                "url": "https://launchpad.net/bugs/1894980"
            },
            {
                "name": "https://launchpad.net/bugs/1900141",
                "refsource": "UBUNTU",
                "url": "https://launchpad.net/bugs/1900141"
            },
            {
                "name": "https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d",
                "refsource": "CONFIRM",
                "url": "https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d"
            },
            {
                "name": "https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f",
                "refsource": "CONFIRM",
                "url": "https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f"
            },
            {
                "name": "https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8",
                "refsource": "CONFIRM",
                "url": "https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8"
            },
            {
                "name": "https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52",
                "refsource": "CONFIRM",
                "url": "https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52"
            },
            {
                "name": "https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84",
                "refsource": "CONFIRM",
                "url": "https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84"
            }
        ]
    },
    "solution": [],
    "source": {
        "advisory": "https://ubuntu.com/USN-4576-1",
        "defect": [
            "https://launchpad.net/bugs/1894980"
        ],
        "discovery": "EXTERNAL"
    },
    "work_around": []
}