CVE-2026-102703
Description
A flaw was found in Xen. When processing batched grant copy operations used for memory sharing between virtual machines, the hypervisor caches internal validation data but fails to properly re-validate it when frame numbers and grant references are intermixed. A malicious guest domain can exploit this flaw by submitting crafted batch requests to bypass memory validation, potentially resulting in unauthorized host memory access, privilege escalation, 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 (2026-11-04) ---
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 re-validation of internal cached validation state in Xen when batched grant copy hypercalls alternate between frame numbers and grant references: upgrade to the fixed Xen builds, which re-validate cached internal state when grant copy operations alternate between frame numbers and grant references, closing crafted batched grant copy hypercall intermixing frame numbers and grant references. Until patched, this is a concern on guest domains running on Xen 4.6 or later with access to grant copy hypercalls, so restrict untrusted users from controlling unprivileged guest domains or executing hypercalls on affected hypervisors, as no standalone configuration workaround is available. These controls limit blast radius and contain exploitation, but they do not fix the underlying improper grant copy cache validation type-confusion defect — apply the upstream patch to fully remediate.
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
When the product accesses the resource using an incompatible type, this could trigger logical errors because the resource does not have expected properties.
Availability,Integrity,Confidentiality
Technical Impact: Read Memory; Modify Memory; Execute Unauthorized Code or Commands; DoS: Crash, Exit, or Restart
If a memory buffer is accessed using an incompatible type, and the allocated buffer is smaller than the type that the code is attempting to access, then an attacker could read or write memory outside the bounds of the buffer, leading to a crash or possibly code execution.
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