{"id":"AZL-6522","summary":"CVE-2020-16120 affecting package kernel for versions less than 5.10.78.1-1","details":"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.","modified":"2026-04-01T05:20:29.907731Z","published":"2021-02-10T20:15:15Z","upstream":["CVE-2020-16120"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-16120"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.78.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-6522.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N"}]}