High [CVE-2026-64286] Clear __hyp_running_vcpu when flushing the pKVM hyp vCPU
This high-severity Red Hat Linux advisory covers CVE-2026-64286 affecting Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Clear __hyp_running_vcpu when flushing the pKVM hyp vCPU flush_hyp_vcpu() copies the host vCPU context into the hyp's private vCPU on every run. ctxt_to_vcpu() expects a guest context to have a NULL __hyp_running_vcpu, which is only ever set on the host context, so that it resolves the vCPU via container_of().
While this is generally the case, flush_hyp_vcpu() copies the context verbatim and does not enforce this, so a value provided by the host is dereferenced at EL2 (host -> EL2). Fix by clearing __hyp_running_vcpu after the copy.
A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) for arm64 architecture. The `flush_hyp_vcpu()` function, responsible for copying the host virtual CPU (vCPU) context, does not properly clear a specific internal pointer (`__hyp_running_vcpu`).
This oversight allows a host to provide a value that is then improperly accessed (dereferenced) at Exception Level 2 (EL2), potentially leading to arbitrary memory access within the hypervisor. This could allow a malicious host to compromise the integrity or availability of the hypervisor.
Red Hat severity: Moderate — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Affected Red Hat products: Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 10 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 10 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 10 days ago·verify at source
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