CVE-2026-89915

CVE CVE-2026-89915EUVD EUVD-2026-80515Published 2026-09-16T10:32:11.000ZLast changed 2026-09-16T14:40:07.000ZCVSS 9.3

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

Linux — Linux 6.16; 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929 <87c2bbf189829dce4aaada8f82e3d54ccc037976; patch: 0; 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929 <5453b85c7ebb605febac3df42021f9471663f051; 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929 <c55bc773b6e814406658fae7dc5c15f639ed816e; patch: 7.2.5; patch: 7.3-rc1; patch: 6.18.52

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

Linux — Linux

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