CVE-2020-14356: 
Sysdig vulnerability analysis and mitigation

A flaw null pointer dereference in the Linux kernel cgroupv2 subsystem in versions before 5.7.10 was found in the way when reboot the system. A local user could use this flaw to crash the system or escalate their privileges on the system (NVD, CVE). The vulnerability was discovered in June 2020 and affects Linux kernel versions prior to 5.7.10.

The vulnerability exists in the cgroup v2 subsystem's handling of socket references to cgroups. In some cgroup configurations, this could lead to a use-after-free condition. The issue was introduced with Linux kernel 4.5 but became more easily reproducible after commit 090e28b ("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged in 5.7.x kernels (Bugzilla). The vulnerability has a CVSS v3.1 base score of 7.8 (High) with vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (Ubuntu).

The vulnerability could allow a local attacker to cause a denial of service (system crash), memory corruption, or potentially escalate privileges to gain administrative access on the system. The issue is particularly impactful when virtual machines or Docker containers are being used (Bugzilla).

The vulnerability can be triggered by a local user without privileges if they have the ability to create/close cgroupv2 or if they create a process attached to an existing cgroupv2 BPF. The issue becomes more reliably exploitable when the system is rebooted (Bugzilla).

The vulnerability was fixed in Linux kernel version 5.7.10 with commit 94886c86e833dbc8995202b6c6aaff592b7abd24. Major Linux distributions have released kernel updates to address this vulnerability. Users should update their systems to patched kernel versions (Ubuntu Security Notice, NetApp Advisory).