CVE Vulnerability

CVE-2020-16120

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.

2.1 /10

CVSS v2.0 :

V3 Legend

Vector :

Exploitability : 3.9 / Impact : 2.9

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Confidentiality Impact PARTIAL

Integrity Impact NONE

Availability Impact NONE

Scope

4.4 /10

CVSS v3.0 : MEDIUM

V3 Legend

Vector :

Exploitability : 0.8 / Impact : 3.6

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required HIGH

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References
Link Resource
https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 Patch Third Party Advisory
https://launchpad.net/bugs/1894980 Issue Tracking Patch
https://ubuntu.com/USN-4578-1 Third Party Advisory
https://www.openwall.com/lists/oss-security/2020/10/14/2 Mailing List Third Party Advisory
https://launchpad.net/bugs/1900141 Issue Tracking Third Party Advisory
https://ubuntu.com/USN-4576-1 Third Party Advisory
https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d Patch Third Party Advisory
https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 Patch Third Party Advisory
https://ubuntu.com/USN-4577-1 Third Party Advisory
https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f Patch Third Party Advisory
https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 Patch Third Party Advisory
Configurations

Configuration 1

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:esm:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*
Information

Published : 2021-02-10 08:15

Updated : 2021-11-18 06:40

NVD link : CVE-2020-16120

Mitre link : CVE-2020-16120

Products Affected
No products.
CWE
NVD-CWE-Other