Medium [CVE-2026-64555] Fix SPSR_EL2 restore in kvm_hyp_handle_mops
This medium-severity Red Hat Linux advisory covers CVE-2026-64555 affecting Red Hat Enterprise Linux 10, 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: nv: Fix SPSR_EL2 restore in kvm_hyp_handle_mops() kvm_hyp_handle_mops() resets the single-step state machine as part of rewinding state for a MOPS exception by modifying vcpu_cpsr() and writing the result directly into hardware.
In the case of nested virtualization, vcpu_cpsr() is a synthetic value such that the rest of KVM can deal with vEL2 cleanly. That means the value requires translation before being written into hardware, which is unfortunately missing from the MOPS handler.
Fix it by directly modifying SPSR_EL2 and avoiding the synthetic state altogether, which will be resynchronized on the next 'full' exit back to KVM. A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) for ARM64 architecture, specifically affecting nested virtualization.
The kvm_hyp_handle_mops() function, responsible for handling certain virtualization operations, incorrectly restored the SPSR_EL2 register. This occurred because a synthetic value used for nested virtualization was written directly to hardware without proper translation, leading to an improper reset of the single-step state machine.
This could potentially impact the stability or security of nested virtualized environments. Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-681.
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 27 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 27 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 27 days ago·verify at source
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