Reference page — cumulative record through Wednesday, October 7, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-3493

CVE-2021-3493HIGH

Ubuntu linux kernel — Linux Kernel

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   L   L   N  C  H  H  H    8.8   .4917   98.9   YES

AFFECTED
  Product       Versions      Fixed
  linux kernel  5.8 kernel –  —

TIMELINE
  Apr 12  Reserved by canonical
  Apr 17  Published (CNA: canonical)
  Oct 20  Added to CISA KEV, remediation due 2022-11-10

CWE-270 · CNA: canonical · CVSS v3.1 · 7 references · KEV due November 10, 2022

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
April 12, 2021	Reserved	Reserved by canonical
April 17, 2021	Published	Published (CNA: canonical)
October 20, 2022	KEV ADDED	Added to CISA KEV, remediation due 2022-11-10

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Ubuntu	linux kernel	—	5.8 kernel	—

Weaknesses

CWE-270

References (7)

http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html [x_refsource_MISC]
http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html [x_refsource_MISC]
http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html [x_refsource_MISC]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52 [x_refsource_MISC]
https://ubuntu.com/security/notices/USN-4917-1 [x_refsource_MISC]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493 [government-resource]
https://www.openwall.com/lists/oss-security/2021/04/16/1 [x_refsource_MISC]

Authoritative record: CVE-2021-3493 at cve.org

Vendors: ubuntu

Weaknesses: CWE-270

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-3493 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, October 7, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.