CVE-2021-3929 is a vulnerability that was discovered in March 2021. This vulnerability affects the Linux kernel and can be exploited by attackers to gain elevated privileges on targeted systems. In practical terms, this means that an attacker with basic user-level access could potentially gain full control of a targeted system by exploiting this vulnerability.
The vulnerability specifically affects the "overlayfs" module in the Linux kernel, which is used to provide a unified view of several file systems. Attackers can exploit the vulnerability by creating a specially crafted file that triggers a buffer overflow when it is opened using overlayfs. This overflow can then be leveraged to execute arbitrary code with elevated privileges.
This vulnerability has been patched in recent versions of the Linux kernel, but organizations running older versions of the kernel may still be at risk. It is therefore recommended that organizations update their Linux kernel to the latest version as soon as possible in order to mitigate the risk of exploitation. Additionally, organizations should implement security best practices such as using firewalls, restricting access to sensitive data, and regularly monitoring system logs for signs of malicious activity.