A flaw was found in the libvirt nwfilter driver. The virNWFilterObjListNumOfNWFilters method failed to acquire the driver->nwfilters mutex before iterating over virNWFilterObj instances. There was no protection to stop another thread from concurrently modifying the driver->nwfilters object. This flaw allows a malicious, unprivileged user to exploit this issue via libvirt's API virConnectNumOfNWFilters to crash the network filter management daemon (libvirtd/virtnwfilterd).
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