Vulnerability intelligence
CVE-2026-42492 and is rated High severity with a CVSS score of 7.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
We have pushed updates to both the Early Access and Normal update channels of each of XenServer 8.4 and XenServer 9. We recommend that customers update to the latest version from their chosen channel following the instructions at https://docs.xenserver.com/en-us/xenserver/8/update or https://docs.xenserver.com/en-us/xenserver/9/update
Xenstore, to have an up-to-date picture of the entire system, wants to know of domains appearing and disappearing. To make this more robust, a new XEN_DOMCTL_get_domain_state was introduced.
The management of the bitmap underlying that operation is tied into the binding of the VIRQ_DOM_EXC virtual IRQ. Unfortunately an error path there would tear down the bitmap even in cases when it wasn't set up.
Unprivileged domains can trigger that error path.
Source: NVD