USN-4915-1

It was discovered that the overlayfs implementation in the Linux kernel did not properly validate the application of file system capabilities with respect to user namespaces. A local attacker could use this to gain elevated privileges. (CVE-2021-3493)

Vincent Dehors discovered that the shiftfs file system in the Ubuntu Linux kernel did not properly handle faults in copy_from_user() when passing through ioctls to an underlying file system. A local attacker could use this to cause a denial of service (memory exhaustion) or execute arbitrary code. (CVE-2021-3492)