CVE-2026-42492
Received Received - Intake

Xenstore Domain State Bitmap Error in Xen Hypervisor

Publication date: 2026-07-28

Last updated on: 2026-07-28

Assigner: Xen Project

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.

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Meta Information

Published
2026-07-28
Last Modified
2026-07-28
Generated
2026-07-28
AI Q&A
2026-07-28
EPSS Evaluated
N/A
NVD
CVE-2026-42492
EUVD
EUVD-2026-49771

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
xen xen From 4.21 (inc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is in Xenstore, a component of the Xen hypervisor that tracks domain states. It involves an error in managing a bitmap tied to the VIRQ_DOM_EXC virtual IRQ. When an error occurs, the bitmap is torn down prematurely even if it wasn't set up correctly. Unprivileged domains can trigger this error path to disrupt Xenstore operations.

Detection Guidance

Detection of CVE-2026-42492 requires checking if your Xen version is 4.21 or later, as this is the affected range. No specific commands are provided in the advisory for detection, but monitoring for Xenstore disruptions or hypervisor crashes may indicate exploitation.

Impact Analysis

This vulnerability can lead to a Denial of Service (DoS) affecting the entire host system. In rare cases, it might also cause a hypervisor crash with similar consequences. Unprivileged domains can exploit this to disrupt Xenstore operations.

Compliance Impact

This vulnerability primarily causes Denial of Service (DoS) conditions or hypervisor crashes, which could disrupt system availability. While it does not directly impact data confidentiality or integrity, prolonged downtime may affect compliance with availability requirements in standards like GDPR or HIPAA.

Mitigation Strategies

Apply the patch provided in XSA-496 advisory immediately. If using Xen 4.21.x, deploy the patch as instructed. For stable branches, check for updates before applying. No other mitigations are known.

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