There are 4 open security issues in buster.
4 issues left for the package maintainer to handle:
qemu/qemu_driver.c in libvirt before 6.0.0 mishandles the holding of a monitor job during a query to a guest agent, which allows attackers to cause a denial of service (API blockage).
A NULL pointer dereference was found in the libvirt API responsible introduced in upstream version 3.10.0, and fixed in libvirt 6.0.0, for fetching a storage pool based on its target path. In more detail, this flaw affects storage pools created without a target path such as network-based pools like gluster and RBD. Unprivileged users with a read-only connection could abuse this flaw to crash the libvirt daemon, resulting in a potential denial of service.
An issue was discovered in qemuDomainGetStatsIOThread in qemu/qemu_driver.c in libvirt 4.10.0 though 6.x before 6.1.0. A memory leak was found in the virDomainListGetStats libvirt API that is responsible for retrieving domain statistics when managing QEMU guests. This flaw allows unprivileged users with a read-only connection to cause a memory leak in the domstats command, resulting in a potential denial of service.
A double free memory issue was found to occur in the libvirt API, in versions before 6.8.0, responsible for requesting information about network interfaces of a running QEMU domain. This flaw affects the polkit access control driver. Specifically, clients connecting to the read-write socket with limited ACL permissions could use this flaw to crash the libvirt daemon, resulting in a denial of service, or potentially escalate their privileges on the system. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
You can find information about how to handle these issues in the security team's documentation.