Bug 2507799 (CVE-2026-64555)

Summary: CVE-2026-64555 kernel: KVM: arm64: nv: Fix SPSR_EL2 restore in kvm_hyp_handle_mops()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
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.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-27 21:05:23 UTC 
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.
Comment 1 TEJ RATHI 2026-07-29 05:11:57 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072738-CVE-2026-64555-037b@gregkh/T