CVE-2021-3493

The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on...

Basic Information

CVE State: PUBLISHED
Reserved Date: April 12, 2021
Published Date: April 17, 2021
Last Updated: February 07, 2025
Vendor: Ubuntu
Product: linux kernel
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.

CVSS Scores

CVSS v3.1

8.8 - HIGH

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

SSVC Information

Exploitation: active
Technical Impact: total

Exploit Status

Exploited in the Wild: Yes (added 2022-10-20 00:00:00 UTC) Source
Proof of Concept Available: Yes (added 2021-05-02 01:58:29 UTC) Source

References

https://ubuntu.com/security/notices/USN-4917-1 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52 https://www.openwall.com/lists/oss-security/2021/04/16/1 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

Known Exploited Vulnerability Information

Source	Added Date
CISA	2022-10-20 00:00:00 UTC

Scanner Integrations

Scanner	URL	Date Detected
Metasploit	https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/local/cve_2021_3493_overlayfs.rb	2025-04-29 11:01:17 UTC

Potential Proof of Concepts

Warning: These PoCs have not been tested and could contain malware. Use at your own risk.

cve_2021_3493_overlayfs

Type: metasploit • Created: Unknown

Metasploit module for CVE-2021-3493

iamz24/CVE-2021-3493_CVE-2022-3357

Type: github • Created: 2024-07-04 17:29:28 UTC • Stars: 0

inspiringz/CVE-2021-3493

Type: github • Created: 2021-07-07 06:16:48 UTC • Stars: 39

CVE-2021-3493 Ubuntu OverlayFS Local Privesc (Interactive Bash Shell & Execute Command Entered)

Abdennour-py/CVE-2021-3493

Type: github • Created: 2021-05-02 01:58:29 UTC • Stars: 0

oneoy/CVE-2021-3493

Type: github • Created: 2021-04-22 02:06:21 UTC • Stars: 3

briskets/CVE-2021-3493

Type: github • Created: 2021-04-19 20:07:01 UTC • Stars: 418

Ubuntu OverlayFS Local Privesc