DEBIAN-CVE-2020-16120

Advisory lineage Upstream: 1 Downstream: 0
Upstream
CVE-2020-16120
Published: 10 Feb 2021, 20:15
Last modified:28 Apr 2026, 20:21

Vulnerability Summary

Overall Risk (default)
low
18/100
CVSS Score
4.4 MEDIUM
3.1 (osv_debian)
EPSS Score
No data
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

10 Feb 2021, 20:15
Published
Vulnerability first disclosed
28 Apr 2026, 20:21
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•MEDIUM•Score: 4.4CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

Affected Systems

  • debian•linux

    < 5.8.7-1 | < 5.8.7-1 | < 5.8.7-1 | < 5.8.7-1

References (1)