CVE-2021-3493 is a vulnerability in Canonical Ubuntu Linux
Published on April 17, 2021
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.
Known Exploited Vulnerability
This Linux Kernel Privilege Escalation Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. 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.
The following remediation steps are recommended / required by November 10, 2022: Apply updates per vendor instructions.
CVE-2021-3493 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. It has an exploitability score of 1.8 out of four. The potential impact of an exploit of this vulnerability is considered to be very high.
What is an AuthZ Vulnerability?
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
CVE-2021-3493 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2021-3493
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What versions of Ubuntu Linux are vulnerable to CVE-2021-3493?
- Canonical Ubuntu Linux Version 18.04.1 Fixed in Version 20.04
- Canonical Ubuntu Linux Fixed in Version 18.04
- Canonical Ubuntu Linux Fixed in Version 20.10