Some OSes (such as Linux, FreeBSD, NetBSD) are processing watch events using a single thread. If the events are received faster than the thread is able to handle, they will get queued. As the queue is unbound, a guest may be able to trigger a OOM in the backend.
External References: https://www.openwall.com/lists/oss-security/2020/12/15/10
Created xen tracking bugs for this issue: Affects: fedora-all [bug 1908084]
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.
This was fixed for Fedora with the 5.10.4 stable kernel updates.