CVE-2021-3493

8.8 HIGH CISA KEV - Actively Exploited
Published: April 17, 2021 Modified: October 28, 2025
View on NVD

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.

AI Explanation

Get an AI-powered plain-language explanation of this vulnerability and remediation steps.

Login to generate AI explanation

CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html
Source: security@ubuntu.com
Exploit Third Party Advisory VDB Entry
http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html
Source: security@ubuntu.com
Press/Media Coverage Third Party Advisory VDB Entry
http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html
Source: security@ubuntu.com
Exploit Third Party Advisory VDB Entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
Source: security@ubuntu.com
Mailing List Patch Third Party Advisory
https://ubuntu.com/security/notices/USN-4917-1
Source: security@ubuntu.com
Vendor Advisory
https://www.openwall.com/lists/oss-security/2021/04/16/1
Source: security@ubuntu.com
Mailing List Third Party Advisory
http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html
Source: af854a3a-2127-422b-91ae-364da2661108
Exploit Third Party Advisory VDB Entry
http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html
Source: af854a3a-2127-422b-91ae-364da2661108
Press/Media Coverage Third Party Advisory VDB Entry
http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html
Source: af854a3a-2127-422b-91ae-364da2661108
Exploit Third Party Advisory VDB Entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List Patch Third Party Advisory
https://ubuntu.com/security/notices/USN-4917-1
Source: af854a3a-2127-422b-91ae-364da2661108
Vendor Advisory
https://www.openwall.com/lists/oss-security/2021/04/16/1
Source: af854a3a-2127-422b-91ae-364da2661108
Mailing List Third Party Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
US Government Resource

13 reference(s) from NVD

Quick Stats

CVSS v3 Score
8.8 / 10.0
EPSS (Exploit Probability)
76.8%
99th percentile
Exploitation Status
Actively Exploited
Remediation due: 2022-11-10

Weaknesses (CWE)

CWE-270 CWE-863

Affected Vendors

canonical

Related CVEs

CVE-2025-52691 10.0
CVE-2025-15168 7.3
CVE-2025-15167 7.3
CVE-2025-15166 7.3
CVE-2025-15165 7.3