CVE-2026-89916

Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source

AV:LAttack vector, local

An arm64 nested L1 hypervisor reaches the bug via KVM_RUN: a VNCR data abort (kvm_handle_vncr_abort → kvm_translate_vncr) races a trapped EL2 TLBI (handle_tlbi_el2 → kvm_handle_s1e2_tlbi → invalidate_vncr_va). This is local KVM ioctl/guest execution, not a network, adjacent-radio, or physical path.

AC:LAttack complexity, low

The attacker owns both vCPUs of the same VM: one walks EL2 stage-1 for VNCR while another updates those S1 page tables and issues TLBI S1E2. A race the attacker drives on both sides is AC:L, and nested virt on NV-capable arm64 hosts is an attacker-selectable deployment.

PR:NPrivileges required, none

Exploitation requires no host root or init-namespace capabilities beyond running hypervisor code in a tenant KVM guest on an arm64 host with nested virtualization enabled; the attacker operates entirely from within their assigned VM, consistent with other arm64 KVM nested-virt CVE scoring.

UI:NUser interaction, none

No victim user or administrator action is required beyond the attacker operating their own nested-virtualization workload; VNCR faults, S1 page-table updates, and TLBI S1E2 on a second vCPU are fully attacker-driven.

S:CScope, changed

The stale VNCR pseudo-TLB is installed in host KVM and mapped into the host per-CPU fixmap via __set_fixmap, so a guest-controlled walk/TLBI race corrupts host nested-MMU state and can retain a writable kernel mapping of a revoked PFN, crossing the guest-to-hypervisor security boundary.

C:HConfidentiality impact, high

kvm_translate_vncr() stores a raw HPA and drops the page pin via kvm_release_faultin_page(). A walk that misses S1 TLBI retry still maps that HPA PAGE_KERNEL in the host VNCR fixmap, so NV2/sysreg emulation can read pages the guest has invalidated and the host may have reused, which is UAF-class disclosure.

I:HIntegrity impact, high

The same stale vncr_tlb is remapped writable (PAGE_KERNEL) in the host fixmap, so nested EL2 register writes and NV2 stores land in the old HPA after the guest's TLBI/BBM sequence. That is a host-kernel write to memory whose translation was revoked and may have been reused.

A:HAvailability impact, high

Using a stale HPA through the host VNCR fixmap can oops or panic the host if the PFN was unmapped or recycled, and corrupting nested EL2 control state or reused host pages can hang or crash the hypervisor and co-resident VMs; the attacker can retrigger the walk/TLBI race.