CVE-2021-3493: Linux Kernel Privilege Escalation Vulnerability
Last updated 27 August 2026
Other sources
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.
— Launchpad
The overlayfs stacking file system in Linux kernel does not properly validate the application of file capabilities against user namespaces, which could lead to privilege escalation.
— CISA
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.180-1Fixed in 6.12.94-1Fixed in 6.12.107-1Fixed in 7.1.12-1
Event History
Frequently Asked Questions
What is the severity of CVE-2021-3493?
CVE-2021-3493 has a high severity rating due to the potential for local privilege escalation through improper validation of file capabilities.
How do I fix CVE-2021-3493?
To fix CVE-2021-3493, upgrade the Linux kernel to versions 5.10.223-1, 5.10.226-1, 6.1.123-1, 6.1.119-1, 6.12.11-1, or 6.12.12-1.
Which versions of Ubuntu are affected by CVE-2021-3493?
CVE-2021-3493 affects Ubuntu versions ranging from 18.04 to 20.10, including specific LTS releases.
Is CVE-2021-3493 a network-related vulnerability?
No, CVE-2021-3493 is a local vulnerability that requires local access to exploit rather than being network-related.
What component of the Linux system does CVE-2021-3493 affect?
CVE-2021-3493 affects the overlayfs implementation within the Linux kernel.