Code paths in Xen's MSI handling have been identified which act on unsanitized values read back from device hardware registers. While devices strictly compliant with PCI specifications shouldn't be able to affect these registers, experience shows that it's very common for devices to have out-of-spec "backdoor" operations which can affect the result of these reads.
Acknowledgments: Name: the Xen project
Statement: Only guests with passed-through PCI devices may be able to leverage this vulnerability. Additionally, only x86 systems are vulnerable. ARM systems are not affected by this flaw. This flaw has been rated as having a security impact of Moderate, and is not currently planned to be addressed in future updates of Red Hat Enterprise Linux 5. Red Hat Enterprise Linux 5 is now in Extended Life Phase of the support and maintenance life cycle. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
Mitigation: Avoid pass-through of physical devices to untrusted guests.
Created xen tracking bugs for this issue: Affects: fedora-all [bug 1881587]
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-25595
External References: https://xenbits.xen.org/xsa/advisory-337.html