Live › vulnerability › CVE-2021-3493
Go to dashboardThe overlayfs file system in the Linux kernel does not properly check file capabilities against user namespaces. A local user can gain root privileges on the machine.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 19:11 UTC, 3h before NVD. All times on this page are UTC.
Apply updates per vendor instructions.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| Linux Kernel | vendor | – | – |
| canonical ubuntu linux | vendor | < 18.04 | 18.04 |
| canonical ubuntu linux | vendor | >= 18.04.1, < 20.04 | 20.04 |
| canonical ubuntu linux | vendor | < 20.10 | 20.10 |
Unknown from the sources.
Apply the kernel update from your Linux distribution vendor; CISA says to apply updates per vendor instructions.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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.
This page as .md · .json · in your agent: get_signal("CVE-2021-3493")
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