# CVE-2021-3493: Linux Kernel Privilege Escalation Vulnerability

> CVE-2021-3493: Linux Kernel Privilege Escalation Vulnerability. CVSS 8.8 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2021-3493
Last updated: 2025-10-21T23:25:48Z

- Published: 2021-04-17 04:20 UTC · Updated: 2025-10-21 23:25 UTC · Assigner: canonical
- CVSS: 8.8 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- EPSS: 49.2%, 99th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2022-10-20, federal due date 2022-11-10, ransomware use: Unknown
- CWE: CWE-270

## 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.

## CISA required action

Apply updates per vendor instructions.

## Affected vendors and products

- Ubuntu: linux kernel

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-3493)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2021-3493)
- [http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html](http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html)
- [http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html](http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html)
- [http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html](http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html)
- [https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52)
- [https://ubuntu.com/security/notices/USN-4917-1](https://ubuntu.com/security/notices/USN-4917-1)
- [https://www.openwall.com/lists/oss-security/2021/04/16/1](https://www.openwall.com/lists/oss-security/2021/04/16/1)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2021-3493 · Markdown: https://rewindex.com/cve/CVE-2021-3493.md · JSON: https://rewindex.com/api/v1/cves/CVE-2021-3493 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:14:52.656Z