CVE-2021-3493: Linux Kernel Privilege Escalation Vulnerability

CVE-2021-3493 · Severity: critical · CVSS 7.8 · Exploited in the wild · Published 2022-10-20

The overlayfs implementation in the Linux kernel fails to properly validate file capabilities against user namespaces. When combined with unprivileged user namespaces and specific Ubuntu kernel patches allowing unprivileged overlay mounts, a local attacker can gain elevated privileges.

Technologies: Linux Kernel. Vendors: Linux.

Quick answers

Is CVE-2021-3493 exploited in the wild?
Yes. CVE-2021-3493 is known to be exploited in the wild, first recorded on 20 October 2022. Treat it as urgent.
How severe is CVE-2021-3493?
Critical severity, with a CVSS score of 7.8, published 20 October 2022.
Which products and versions are affected?
Linux Linux Kernel Ubuntu kernel patches for unprivileged overlay mounts.
Is there a fix for CVE-2021-3493?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2021-3493 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2021-3493?
Check whether you run Linux Kernel. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Affected products

  • Linux Linux Kernel Ubuntu kernel patches for unprivileged overlay mounts

Timeline

  • 2021-04-16: disclosed: Public disclosure on oss-security mailing list
  • 2022-10-20: kev added: Added to CISA Known Exploited Vulnerabilities Catalog

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