CISA KEV · Known exploitedHigh

CVE-2021-3493

Linux Kernel

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: 7.8
EPSS: 49.2%
CISA KEV: Listed
Published: 2021.04.17

PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV

Exploit probability49.2%

Technical severityCVSS 7.8

Vulnerability overview

Affected product and versions

Product: Linux Kernel
Affected versions: 5.8 kernel, 5.4 kernel, 4.15 kernel, 4.4 kernel, < 18.04, >= 18.04.1 < 20.04, < 20.10
Fixed versions: 18.04, 20.04, 20.10

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

CISA required action

Apply updates per vendor instructions.

Due date: 2022.11.10

1
Identify
Confirm that Linux Kernel and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-270, CWE-862, CWE-863
KEV added: 2022.10.20
Ransomware use: 미확인