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 26 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 26 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 26 days ago·verify at source
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