What is CVE-2021-3493?

CVE-2021-3493 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10. CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild.

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

CVE-2021-3493 has a CVSS score of 7.8 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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

No patch is currently available for CVE-2021-3493. Monitor the NIST NVD and your Linux distribution's security advisories for updates.

Is CVE-2021-3493 actively exploited?

Yes — CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild with a CVSS score of 7.8 (High severity).

CVE-2021-3493

High KEV — Actively Exploited

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.

Package Linux Kernel

Published 2021-04-17

Last modified 2025-10-28

CVSS version 3.1

Patch available

Awaiting data

CVSS 3.1 score

7.8

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

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

Weakness type

CWE-270

CVE-2021-3493 is classified as CWE-270

See CWE-270 on MITRE CWE for full details on this weakness type.

References

The following references provide additional information about CVE-2021-3493 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Packet Storm
http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html

Exploit Third Party Advisory VDB Entry
Packet Storm
http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html

Press/Media Coverage Third Party Advisory VDB Entry
Packet Storm
http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html

Exploit Third Party Advisory VDB Entry
Ubuntu Security
https://ubuntu.com/security/notices/USN-4917-1

Vendor Advisory
Openwall
https://www.openwall.com/lists/oss-security/2021/04/16/1

Mailing List Third Party Advisory
CISA
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493

US Government Resource
Kernel patch commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
Patch

Details

CVE ID CVE-2021-3493

Severity High

CVSS score 7.8 / 10

CVSS version 3.1

Published 2021-04-17

Modified 2025-10-28

KEV Yes

Patch Awaiting data

Package linux

Frequently asked questions

What is CVE-2021-3493?

CVE-2021-3493 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 . CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild.
What is the CVSS score for CVE-2021-3493?

CVE-2021-3493 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2021-3493?

No patch is currently available for CVE-2021-3493. Monitor the NIST NVD and your Linux distribution's security advisories for updates.
Is CVE-2021-3493 actively exploited?

Yes — CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. It carries a CVSS score of 7.8 (High severity).