CVE-2026-63940 (GCVE-0-2026-63940)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-07-20 13:41
VLAI
Title
KVM: SEV: Ignore Port I/O requests of length '0'
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Ignore Port I/O requests of length '0' Explicitly ignore Port I/O requests of length '0' (or count '0'), so that setting up the software scratch area (and other code) doesn't have to worry about underflowing the length, and to allow for WARNing on trying to configure the scratch area with len==0.
Severity
9.3 (Critical)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 291bd20d5d88814a73d43b55b9428feab2f28094 , < 3b6035bc6bff20e89752ce4358bc4c9a9d5883f2 (git)
Affected: 291bd20d5d88814a73d43b55b9428feab2f28094 , < 2254972d4d69e279ba4e87bf0968eb08ad0d3c92 (git)
Affected: 291bd20d5d88814a73d43b55b9428feab2f28094 , < c30cde934c7813b4e3069765dac64ce3d31e34f2 (git)
Affected: 291bd20d5d88814a73d43b55b9428feab2f28094 , < 3988bd2723de407ae90fa7a6f6029b4e60238c58 (git)
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Linux Linux Affected: 5.11
Unaffected: 0 , < 5.11 (semver)
Unaffected: 6.12.95 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Ignore Port I/O requests of length \u00270\u0027\n\nExplicitly ignore Port I/O requests of length \u00270\u0027 (or count \u00270\u0027), so that\nsetting up the software scratch area (and other code) doesn\u0027t have to\nworry about underflowing the length, and to allow for WARNing on trying\nto configure the scratch area with len==0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.3,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
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      "providerMetadata": {
        "dateUpdated": "2026-07-20T13:41:42.039Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/3988bd2723de407ae90fa7a6f6029b4e60238c58"
        }
      ],
      "title": "KVM: SEV: Ignore Port I/O requests of length \u00270\u0027",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63940",
    "datePublished": "2026-07-19T14:55:36.408Z",
    "dateReserved": "2026-07-19T07:54:57.022Z",
    "dateUpdated": "2026-07-20T13:41:42.039Z",
    "state": "PUBLISHED"
  },
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  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-63940",
      "date": "2026-07-21",
      "epss": "0.00182",
      "percentile": "0.08051"
    },
    "microsoft_vex": {
      "current_release_date": "2026-07-21T01:03:02.000Z",
      "cve": "CVE-2026-63940",
      "id": "msrc_CVE-2026-63940",
      "initial_release_date": "2026-07-21T01:03:02.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "KVM: SEV: Ignore Port I/O requests of length \u00270\u0027",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63940.json",
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    },
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  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.