CVE-2021-3493 : Security Advisory and Response
Learn about CVE-2021-3493, a high-impact security vulnerability in the Linux kernel affecting Ubuntu systems. Find out the impact, affected versions, and mitigation steps.
This article provides details about CVE-2021-3493, a security vulnerability in the Linux kernel affecting Ubuntu systems.
Understanding CVE-2021-3493
CVE-2021-3493 is related to the overlayfs implementation in the Linux kernel, impacting Ubuntu systems. It was reported by an independent security researcher to the SSD Secure Disclosure program.
What is CVE-2021-3493?
The vulnerability in the overlayfs implementation in the Linux kernel allowed an attacker to gain elevated privileges by exploiting the improper validation of file capabilities in user namespaces, combined with unprivileged overlay mounts in the Ubuntu kernel.
The Impact of CVE-2021-3493
The impact of this vulnerability is rated as high, with a base severity score of 8.8 (High) according to the CVSS v3.1 metrics. It could lead to the compromise of confidentiality, integrity, and availability of affected systems.
Technical Details of CVE-2021-3493
The following technical details shed light on the vulnerability:
Vulnerability Description
The Linux kernel's improper validation of file capabilities within user namespaces could be exploited for privilege escalation by malicious actors.
Affected Systems and Versions
Ubuntu systems running Linux kernel versions less than 5.8.0-50.56, 5.4.0-72.80, 4.15.0-142.146, and 4.4.0-209.241 are affected by this vulnerability.
Exploitation Mechanism
By leveraging unprivileged user namespaces and the Ubuntu kernel's unprivileged overlay mounts feature, an attacker could exploit this vulnerability to elevate their privileges.
Mitigation and Prevention
To address CVE-2021-3493, the following mitigation strategies can be implemented:
Immediate Steps to Take
Disable unprivileged user namespaces as a temporary workaround measure.
Long-Term Security Practices
Regularly update the Linux kernel to patched versions and follow security best practices to prevent privilege escalation attacks.
Patching and Updates
Apply the necessary security patches provided by Ubuntu to mitigate the vulnerability.