CVE-2026-42492: vIRQ event channel binding may break Xenstore

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-28 · updated 2026-07-28
Weakness: CWE-459

Description

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.

References

https://xenbits.xenproject.org/xsa/advisory-496.html
http://www.openwall.com/lists/oss-security/2026/07/28/13
http://xenbits.xen.org/xsa/advisory-496.html

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