CVE-2021-3493Linux Kernel Privilege Escalation Vulnerability

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.

8.8 HIGHEPSS 49.16%⚡ Known Exploited (CISA KEV)NVD: Analyzed

Last updated: 2026-06-17 04:05 UTC

OverviewCVSS details

8.8HIGHCVSS 3.1

Score source: canonical (CNA)
NVD status: Analyzed
Published: Apr 17, 2021
Assigner: canonical

Affected

linux kernel (Ubuntu)

Versions: 5.8 kernel before 5.8.0-50.56 · 5.4 kernel before 5.4.0-72.80
Fixed in: 5.8.0-50.56, 5.4.0-72.80, 4.15.0-142.146

All affected versions →

Exploitation

Public exploit: Yes · 2 references
CISA KEV: Listed · Oct 20, 2022
KEV due date: Nov 10, 2022
Ransomware use: Unknown
SSVC: Exploitation active · Automatable no · Impact total

EPSS · FIRST, scored Nov 7

49.16%chance of exploitation in 30 days

Higher than 98.89% of CVEs

CVSS 3.1 · canonical (CNA)

8.8High

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

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Changed
Confidentiality impact: High
Integrity impact: High
Availability impact: High

CVSS 3.1 · NVD

7.8High

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

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

CVSS 2.0 · NVD

7.2High

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

Attack vector: Local
Attack complexity: Low
Authentication: None
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

NVD status: Analyzed

Overview Affected Products References

NVD CVE.org

Overview

Severity

Score	Severity	Version	Vector String
8.8	HIGH	3.1canonical (CNA)	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
7.8	HIGH	3.1NVD	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2	HIGH	2.0NVD	AV:L/AC:L/Au:N/C:C/I:C/A:C

CISA required action

⚡ Known exploited · remediation due Nov 10, 2022

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Details

CVE ID: CVE-2021-3493
Status: Analyzed
Assigner (CNA): canonical
Published: Apr 17, 2021
Last modified: 2026-06-17 04:05 UTC
Weaknesses: CWE-270 · Privilege Context Switching Error
CWE-863
CWE-862

Sources

Refreshed hourly from the sources above. Last fetched 2026-11-08 14:24 UTC.