FKIE_CVE-2026-89915

Vulnerability from fkie_nvd - Published: 2026-09-16 11:17 - Updated: 2026-09-16 15:18
Severity
9.3 (Critical) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5453b85c7ebb605febac3df42021f9471663f051
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/87c2bbf189829dce4aaada8f82e3d54ccc037976
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c55bc773b6e814406658fae7dc5c15f639ed816e
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/arm64/include/asm/kvm_host.h",
            "arch/arm64/kvm/hyp/vhe/switch.c",
            "arch/arm64/kvm/nested.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5453b85c7ebb605febac3df42021f9471663f051",
              "status": "affected",
              "version": "4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929",
              "versionType": "git"
            },
            {
              "lessThan": "87c2bbf189829dce4aaada8f82e3d54ccc037976",
              "status": "affected",
              "version": "4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929",
              "versionType": "git"
            },
            {
              "lessThan": "c55bc773b6e814406658fae7dc5c15f639ed816e",
              "status": "affected",
              "version": "4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/arm64/include/asm/kvm_host.h",
            "arch/arm64/kvm/hyp/vhe/switch.c",
            "arch/arm64/kvm/nested.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Remove VM-wide VNCR mapping counter\n\nThe global VNCR mapping counter is used to decide whether an L1\nprovided VNCR page is mapped in L0 on any CPU at the point of\ndealing with a TLB invalidation. It is incremented when a mapping\nis made in the fixmap, and decremented when unmapped.\n\nAs it turns out, this tracking has several flaws:\n\n- we are trying to invalidate TLBs, and the mapping is only an\n  opportunistic consequence of the TLB. Checking this counter to\n  decide whether a TLB needs to be invalidated may result in missed\n  invalidations.\n\n- an L1 vcpu invalidating its own TLB (a very likely case) will not\n  succeed in invalidating the VNCR pseudo TLB because that page is\n  not mapped in L0 at this stage.\n\nGiven that this tracking fails at delivering the minimum guarantees\nthat are required and is only a performance optimisation, remove it\ncompletely."
    }
  ],
  "id": "CVE-2026-89915",
  "lastModified": "2026-09-16T15:18:17.760",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 9.3,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.5,
        "impactScore": 6.0,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-16T11:17:00.553",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5453b85c7ebb605febac3df42021f9471663f051"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/87c2bbf189829dce4aaada8f82e3d54ccc037976"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c55bc773b6e814406658fae7dc5c15f639ed816e"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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