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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." } ], "metrics": [ { "cvssV3_1": { "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" } } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-266", "description": "CWE-266 Incorrect Privilege Assignment", "lang": "en", "type": "CWE" } ] } ], "providerMetadata": { "dateUpdated": "2021-02-10T19:45:26", "orgId": "cc1ad9ee-3454-478d-9317-d3e869d708bc", "shortName": "canonical" }, "references": [ { "tags": [ "vendor-advisory", "x_refsource_UBUNTU" ], "url": "https://ubuntu.com/USN-4576-1" }, { "tags": [ "vendor-advisory", "x_refsource_UBUNTU" ], "url": "https://ubuntu.com/USN-4577-1" }, { "tags": [ "vendor-advisory", "x_refsource_UBUNTU" ], "url": "https://ubuntu.com/USN-4578-1" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://www.openwall.com/lists/oss-security/2020/10/14/2" }, { "tags": [ "vendor-advisory", "x_refsource_UBUNTU" ], "url": "https://launchpad.net/bugs/1894980" }, { "tags": [ "vendor-advisory", "x_refsource_UBUNTU" ], "url": "https://launchpad.net/bugs/1900141" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52" }, { "tags": [ "x_refsource_CONFIRM" ], "url": "https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84" } ], "source": { "advisory": "https://ubuntu.com/USN-4576-1", "defect": [ "https://launchpad.net/bugs/1894980" ], "discovery": "EXTERNAL" }, "title": "Unprivileged overlay + shiftfs read access", "x_generator": { "engine": "Vulnogram 0.0.9" }, "x_legacyV4Record": { "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. 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