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CVE-2026-23556 is a denial-of-service vulnerability in Xen environments using oxenstored, the OCaml implementation of xenstored. During domain teardown, oxenstored correctly removes xenstore node data for the destroyed domain but fails to clear the associated quota-related usage counters. If that domain ID is later reused, the replacement domain inherits stale accounting state and is treated as having already consumed part of its xenstore quota. As leaked counts accumulate across repeated domain destruction and ID reuse, newly created domains can create progressively fewer xenstore nodes before being considered over quota, eventually preventing normal operation. The issue affects Xen versions that include the XSA-419 fixes when configured to use oxenstored; systems using the C implementation, xenstored, are not affected.
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A vulnerability in Xen oxenstored where usage counts are leaked during domain teardown, causing a reused domain ID to inherit reduced node quota availability.
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 flaw in oxenstored where quota-related use counts persist across domain destruction, enabling a privileged guest-domain user to cause denial of service by preventing other domains from starting.
A Xen/oxenstored flaw where quota-related use counts persist across domain destruction, enabling a privileged guest VM user to cause host denial of service.
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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.
Community discussion across Reddit, Mastodon, and other social sources.