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CVE-2026-23558 is a race condition in Xen grant table v2 status page handling affecting Xen 4.0 and later. The flaw occurs on x86 when an HVM or PVH guest changes the grant table version from v2 to v1 concurrently with mapping grant status pages through XENMEM_add_to_physmap. Under this race, some status pages can be freed while mappings to those pages are still inserted into the guest's secondary P2M page tables, creating a use-after-free condition. The issue remained after earlier fixes associated with XSA-379 and XSA-387. The vulnerability is specific to environments where grant table v2 is available to HVM or PVH guests; x86 PV guests cannot leverage it, and Arm is not affected because grant table v2 is unsupported there.
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A Citrix-addressed vulnerability listed in the July 1, 2026 security updates affecting Citrix products; specific technical details are not provided in the content.
A race condition and use-after-free flaw in grant table v2 status page mapping that could let a privileged HVM or PVH guest-domain user escalate privileges to the hypervisor.
A race condition in Xen grant table v2 status page mapping that could allow a privileged guest VM user to compromise the host in certain conditions.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
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