CVE-2026-102704
Description
A flaw was found in Xen. An unprivileged guest domain can bypass memory isolation controls during batched grant copy operations, which are used to share memory between virtual machines. Due to a misplaced validation check when reusing cached memory verification details, Xen permits memory copying by frame number outside of the caller's own assigned memory. A malicious guest could exploit this vulnerability to read or overwrite unauthorized memory, potentially leading to privilege escalation, information disclosure, or a denial of service (DoS).
Statement
Red Hat Product Security has determined that this vulnerability does not affect any currently supported Red Hat product. This assessment may evolve based on further analysis and discovery. For more information about this vulnerability and the products it affects, please see the linked references.
Mitigation
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to enforce caller memory ownership verification on cached grant copy operations across Xen guest hypercall interfaces: upgrade to the fixed Xen builds, which re-validate caller memory ownership before reusing cached grant copy verification details, closing all 2 injection vectors (batched grant copy hypercalls, frame number memory copy targeting foreign domains). Until patched, this is only a concern on Xen hypervisors version 4.6 or later running unprivileged guest domains capable of issuing hypercalls — Xen 4.5 and earlier are unaffected — so restrict untrusted access to guest virtual machines capable of issuing hypercalls, as no vendor workarounds exist. These controls limit blast radius and contain exploitation, but they do not fix the underlying misplaced grant copy validation defect — apply the upstream patch to fully remediate.
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity
An attacker could gain unauthorized access to system resources.
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