gsd-2020-16120
Vulnerability from gsd
Modified
2023-12-13 01:21
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.
Aliases
Aliases
CVE-2020-16120


To clipboard 

{
   GSD: {
      alias: "CVE-2020-16120",
      description: "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.",
      id: "GSD-2020-16120",
      references: [
         "https://www.suse.com/security/cve/CVE-2020-16120.html",
         "https://ubuntu.com/security/CVE-2020-16120",
         "https://security.archlinux.org/CVE-2020-16120",
         "https://linux.oracle.com/cve/CVE-2020-16120.html",
      ],
   },
   gsd: {
      metadata: {
         exploitCode: "unknown",
         remediation: "unknown",
         reportConfidence: "confirmed",
         type: "vulnerability",
      },
      osvSchema: {
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         id: "GSD-2020-16120",
         modified: "2023-12-13T01:21:46.615179Z",
         schema_version: "1.4.0",
      },
   },
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            TITLE: "Unprivileged overlay + shiftfs read access",
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         impact: {
            baseMetricV2: {
               acInsufInfo: false,
               cvssV2: {
                  accessComplexity: "LOW",
                  accessVector: "LOCAL",
                  authentication: "NONE",
                  availabilityImpact: "NONE",
                  baseScore: 2.1,
                  confidentialityImpact: "PARTIAL",
                  integrityImpact: "NONE",
                  vectorString: "AV:L/AC:L/Au:N/C:P/I:N/A:N",
                  version: "2.0",
               },
               exploitabilityScore: 3.9,
               impactScore: 2.9,
               obtainAllPrivilege: false,
               obtainOtherPrivilege: false,
               obtainUserPrivilege: false,
               severity: "LOW",
               userInteractionRequired: false,
            },
            baseMetricV3: {
               cvssV3: {
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                  attackVector: "LOCAL",
                  availabilityImpact: "NONE",
                  baseScore: 4.4,
                  baseSeverity: "MEDIUM",
                  confidentialityImpact: "HIGH",
                  integrityImpact: "NONE",
                  privilegesRequired: "HIGH",
                  scope: "UNCHANGED",
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               exploitabilityScore: 0.8,
               impactScore: 3.6,
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         },
         lastModifiedDate: "2021-11-18T18:40Z",
         publishedDate: "2021-02-10T20:15Z",
      },
   },
}


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