Bug 2507129 (CVE-2026-64287)

Summary: CVE-2026-64287 kernel: KVM: arm64: Bound used_lrs when flushing the pKVM hyp vCPU
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
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 Kernel-based Virtual Machine (KVM) component of the Linux kernel on ARM64 systems. A highly privileged local attacker could exploit a vulnerability where the system fails to properly restrict memory access during a specific virtual machine operation. This could allow the attacker to read or write to sensitive memory areas, potentially leading to privilege escalation, where they gain unauthorized higher access, or cause a system crash (denial of service).
 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 2026-07-25 10:06:34 UTC 
In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Bound used_lrs when flushing the pKVM hyp vCPU

flush_hyp_vcpu() copies the host vGIC state into the hyp's private vCPU
on every run. The vGIC list register save and restore use used_lrs as
their loop bound and expect it to stay within the number of implemented
list registers. While this is generally the case, flush_hyp_vcpu()
copies vgic_v3 verbatim and does not enforce this, so a value provided
by the host is used at EL2 to index vgic_lr[] and access ICH_LR<n>_EL2
(host -> EL2).

Fix by clamping used_lrs to the number of implemented list registers
after the copy, as the trusted path already does in
vgic_flush_lr_state(). The number of implemented list registers is
constant after init, so it is replicated once from
kvm_vgic_global_state.nr_lr into hyp_gicv3_nr_lr rather than read on
every entry.
Comment 1 TEJ RATHI 2026-07-29 16:10:58 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072503-CVE-2026-64287-ea42@gregkh/T