CVE-2026-89915

9.3 CRITICAL

Published 2026-09-16 · Updated 2026-09-16

AI risk analysis

Summary: The flaw lies in the global VNCR mapping counter used for TLB invalidation in the Linux kernel's KVM arm64 implementation, leading to potential missed invalidations and failure to invalidate VNCR pseudo TLBs.
Exploitability: Exploitation is moderately difficult requiring specific conditions, such as an L1 vCPU invalidating its own TLB.
Blast radius: If exploited, the impact could be severe, potentially leading to unauthorized access or execution of code in the KVM environment.
Detection: No reliable host or network indicator is derivable from the published description.
Prioritized remediation: Upgrade to the fixed version 5.19.10 or later.

kernelvulnerabilitykvmarm64tlbinvalidation

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD description

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Remove VM-wide VNCR mapping counter The global VNCR mapping counter is used to decide whether an L1 provided VNCR page is mapped in L0 on any CPU at the point of dealing with a TLB invalidation. It is incremented when a mapping is made in the fixmap, and decremented when unmapped. As it turns out, this tracking has several flaws: - we are trying to invalidate TLBs, and the mapping is only an opportunistic consequence of the TLB. Checking this counter to decide whether a TLB needs to be invalidated may result in missed invalidations. - an L1 vcpu invalidating its own TLB (a very likely case) will not succeed in invalidating the VNCR pseudo TLB because that page is not mapped in L0 at this stage. Given that this tracking fails at delivering the minimum guarantees that are required and is only a performance optimisation, remove it completely.

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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