What is the CVSS score of CVE-2021-3493?

CVE-2021-3493 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 44.0%.

Is there a public PoC exploit available for CVE-2021-3493?

Yes, a public proof-of-concept exploit is available for CVE-2021-3493. Prioritise patching immediately. EPSS: 44.0%.

Is there a patch available for CVE-2021-3493?

Yes, a patch is available for CVE-2021-3493. Update the affected software to the latest version immediately.

Ubuntu CVE-2021-3493

HIGH

Privilege Context Switching Error (CWE-270)

2021-04-17 security@ubuntu.com

Information Disclosure Linux Ubuntu Canonical Ubuntu Linux

7.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-270 ASVS 5.0 V8 - Authorization Privilege context switching
Impact	CVSS score of 7.8 (HIGH). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	Successful exploitation could compromise the high-severity affected system.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 44.0% exploitation probability (EPSS)

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AnalysisAI

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. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-270. 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. Affected products include: Canonical Ubuntu Linux.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.8 HIGH

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Jul 14, 2026 - 04:22 CISA

CVE Published

Apr 17, 2021 - 05:15 nvd

HIGH 7.8

DescriptionNVD

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.

Threat Intelligence Overview

EPSS Score

44.0%

Top 1% exploitable

Exploit

POC

Public exploit code exists

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

CISA KEV

EPSS POC (1)

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV Yes

Public POC Yes

EPSS 44.0%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Out-of-Cycle

Exploitation· derived

Active

System Exposure· derived

Small

Automatable· derived

Human Impact· derived

High

Priority Score

168

Low Medium High Critical

KEV: +50

EPSS: +44

CVSS: +39

PoC: +20

Weaponized: +15

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.