CVE-2021-3493

high

Description

The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.

References

https://www.openwall.com/lists/oss-security/2021/04/16/1

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52

https://ubuntu.com/security/notices/USN-4917-1

http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html

http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html

http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html

Details

Source: MITRE

Published: 2021-04-17

Updated: 2021-12-16

Type: CWE-269

Risk Information

CVSS v2

Base Score: 7.2

Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C

Impact Score: 10

Exploitability Score: 3.9

Severity: HIGH

CVSS v3

Base Score: 7.8

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Impact Score: 5.9

Exploitability Score: 1.8

Severity: HIGH