A potential DoS flaw was found in the virtio-fs shared file system daemon (virtiofsd) implementation of the QEMU version >= v5.0. Virtio-fs is meant to share a host file system directory with a guest via virtio-fs device. If the guest opens the maximum number of file descriptors under the shared directory, a denial of service may occur. This flaw allows a guest user/process to cause this denial of service on the host.
https://www.openwall.com/lists/oss-security/2020/05/04/1
https://security.gentoo.org/glsa/202011-09
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg00143.html
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg00141.html