CVE-2020-16120

CVE Details

Release Date:

2021-02-10

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.

See more information about CVE-2020-16120 from MITRE CVE dictionary and NIST NVD

CVSS v3.0 metrics

NOTE: The following CVSS v3.0 metrics and score provided are preliminary and subject to review.

Base Score:	4.4	Base Metrics:	AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Access Vector:	Local network	Attack Complexity:	Low
Privileges Required:	High	User Interaction:	None
Scope:	Unchanged	Confidentiality Impact:	High
Integrity Impact:	None	Availability Impact:	None

Errata information

Platform	Errata	Release Date
Oracle Linux version 7 (kernel-uek)	ELSA-2021-9084	2021-03-12
Oracle Linux version 7 (kernel-uek-container)	ELSA-2021-9086	2021-03-09
Oracle Linux version 7 (kernel-uek-container)	ELSA-2021-9087	2021-03-09
Oracle Linux version 8 (kernel-uek)	ELSA-2021-9085	2021-03-11
Oracle Linux version 8 (kernel-uek-container)	ELSA-2021-9086	2021-03-09

This page is generated automatically and has not been checked for errors or omissions. For clarification or corrections please contact the Oracle Linux ULN team