CVE-2021-22600: 
Linux Kernel vulnerability analysis and mitigation

A double free vulnerability (CVE-2021-22600) was discovered in the Linux kernel's packet socket (AFPACKET) implementation, specifically in the packetsetring() function within net/packet/afpacket.c. The vulnerability was identified by the syzbot tool and disclosed in January 2022. This security flaw affects Linux kernel versions prior to 5.4.168, 5.10 prior to 5.10.88, and 5.15 prior to 5.15.11 (NVD, Ubuntu).

The vulnerability stems from a double free bug in the packetsetring() function located in net/packet/af_packet.c. The issue occurs when handling packet socket operations, where memory is incorrectly freed twice. The vulnerability has been assigned a CVSS score of 7.8 (HIGH) with the vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating local access requirements but high potential impact (NetApp).

When successfully exploited, this vulnerability can lead to multiple severe consequences including privilege escalation, denial of service through system crashes, memory corruption, and potential arbitrary code execution. The vulnerability is particularly concerning as it affects the kernel level, potentially compromising the entire system's security (Debian).

The primary mitigation is to upgrade the kernel to versions that include the fix (post 5.4.168, 5.10.88, or 5.15.11) or apply the patch with commit ID ec6af094ea28f0f2dda1a6a33b14cd57e36a9755. Various Linux distributions have released security updates to address this vulnerability, including Ubuntu, which has fixed it in versions 5.13.0-30.33 for 21.10 and 5.4.0-100.113 for 20.04 LTS (Ubuntu).