FKIE_CVE-2026-63937

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-20 15:16
Severity
8.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Use READ_ONCE() when reading entries/indices from PSC buffer Use READ_ONCE() when reading entries/indices from the guest-accessible Page State Change buffer to defend against TOCTOU bugs. Don't bother with READ_ONCE()/WRITE_ONCE() for cases where KVM is writing (and not consuming the result!), as the guest isn't supposed to touch the buffer while it's being processed. I.e. using READ_ONCE() is all about protecting against misbehaving guests.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b1dfaa6f7a957726a6800135be3659fbe4bbf2a4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bd232801ef1d1fd985d2d4ca3cd1d888303ca86f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c8cc238093ca6c99267032f6cfe78f59389f3157
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/edbbe88f83b524434974e84808d3093199d67c24
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "bd232801ef1d1fd985d2d4ca3cd1d888303ca86f",
              "status": "affected",
              "version": "9b54e248d2644be71cb394eb85f31ad99e023a05",
              "versionType": "git"
            },
            {
              "lessThan": "b1dfaa6f7a957726a6800135be3659fbe4bbf2a4",
              "status": "affected",
              "version": "9b54e248d2644be71cb394eb85f31ad99e023a05",
              "versionType": "git"
            },
            {
              "lessThan": "edbbe88f83b524434974e84808d3093199d67c24",
              "status": "affected",
              "version": "9b54e248d2644be71cb394eb85f31ad99e023a05",
              "versionType": "git"
            },
            {
              "lessThan": "c8cc238093ca6c99267032f6cfe78f59389f3157",
              "status": "affected",
              "version": "9b54e248d2644be71cb394eb85f31ad99e023a05",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.11"
            },
            {
              "lessThan": "6.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "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: SEV: Use READ_ONCE() when reading entries/indices from PSC buffer\n\nUse READ_ONCE() when reading entries/indices from the guest-accessible\nPage State Change buffer to defend against TOCTOU bugs.\n\nDon\u0027t bother with READ_ONCE()/WRITE_ONCE() for cases where KVM is writing\n(and not consuming the result!), as the guest isn\u0027t supposed to touch the\nbuffer while it\u0027s being processed.  I.e. using READ_ONCE() is all about\nprotecting against misbehaving guests."
    }
  ],
  "id": "CVE-2026-63937",
  "lastModified": "2026-07-20T15:16:57.457",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.0,
        "impactScore": 6.0,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T16:17:12.193",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b1dfaa6f7a957726a6800135be3659fbe4bbf2a4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bd232801ef1d1fd985d2d4ca3cd1d888303ca86f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c8cc238093ca6c99267032f6cfe78f59389f3157"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/edbbe88f83b524434974e84808d3093199d67c24"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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