What is CVE-2021-3493?

CVE-2021-3493 is a high-severity vulnerability in Canonical Ubuntu_linux, classified under Privilege Context Switching Error. CVSS score: 8.8/10. Published 2021-04-17.

How severe is CVE-2021-3493?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2021-3493 known to be exploited?

Yes. CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-10-20), indicating it is being actively exploited. 212 public proof-of-concept repositories are indexed.

Auth bypass in Canonical Ubuntu_linux

CVE-2021-3493

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…

EPSS: 0.440 (98.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

Affected products

Canonical Ubuntu_linux
Ubuntu Linux Kernel — versions 5.8 kernel, 5.4 kernel, 4.15 kernel

Weakness classification (CWE)

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-10-20. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-11-10.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

security@ubuntu.com (x_refsource_MISC, Vendor Advisory)
security@ubuntu.com (Patch, Mailing List, Third Party Advisory, x_refsource_MISC)
security@ubuntu.com (Mailing List, Third Party Advisory, x_refsource_MISC)
security@ubuntu.com (Exploit, VDB Entry, Third Party Advisory, x_refsource_MISC)
security@ubuntu.com (VDB Entry, Third Party Advisory, x_refsource_MISC, Press/Media Coverage)
security@ubuntu.com (Exploit, VDB Entry, Third Party Advisory, x_refsource_MISC)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2021-3493?: CVE-2021-3493 is a high-severity vulnerability in Canonical Ubuntu_linux, classified under Privilege Context Switching Error. CVSS score: 8.8/10. Published 2021-04-17.
How severe is CVE-2021-3493?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2021-3493 known to be exploited?: Yes. CVE-2021-3493 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-10-20), indicating it is being actively exploited. 212 public proof-of-concept repositories are indexed.