xen/gntalloc: validate grant count before allocation

{
  "id": "6b42c9e4ca03fb37e7ab58a19f7b62a9db3e2bbd4c5cc3f1eca1e9f5ff74f51b",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-98900",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "xen/gntalloc: validate grant count before allocation",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: xen/gntalloc: validate grant count before allocation gntalloc_ioctl_alloc() allocates the grant-id array before checking whether the requested count fits within the global grant limit. Counts above that limit cannot succeed, so reject them before the user-controlled allocation reaches kcalloc(). Use a subtraction-based check while holding gref_mutex so adding the requested count cannot wrap. Also cast the count before advancing the per-file index so the page-size multiplication is performed in 64-bit arithmetic.",
    "evidence": "cve:CVE-2026-98900",
    "products": [
      {
        "name": {
          "value": "Linux",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      },
      {
        "name": {
          "value": "Linux",
          "evidence": "/containers/cna/affected/1/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98900",
      "aliases": [
        "CVE-2026-98900"
      ],
      "metrics": [],
      "affected": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "e2806390aa1c4d5b3f7a68f10a56ae12c71c00d8",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "71a0cf87e19fb35c4292ca88985e376e613c900a",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "641de086a05f349de7fc548612432bc2fed721ca",
              "versionType": "git"
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            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "720554c04acba80018ded069d3e0984bebaee891",
              "versionType": "git"
            },
            {
              "status": "affected",
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              "lessThan": "84d5727cef8eb9c8a28210ad248f1c70b223b065",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "231542f4e43cf9837cb520664545e85fbe666b7b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "dd3140588d9551235ebc2a0dacdca098e7677573",
              "lessThan": "2299822f3f466b5dcad2377bf63986199f881a6b",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/xen/gntalloc.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.39"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "2.6.39",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.10.271",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/xen/gntalloc.c"
          ],
          "defaultStatus": "affected"
        }
      ],
      "modified": "2026-10-26T06:56:27.943Z",
      "provider": "cve",
      "references": [
        "https://git.kernel.org/stable/c/e2806390aa1c4d5b3f7a68f10a56ae12c71c00d8",
        "https://git.kernel.org/stable/c/71a0cf87e19fb35c4292ca88985e376e613c900a",
        "https://git.kernel.org/stable/c/641de086a05f349de7fc548612432bc2fed721ca",
        "https://git.kernel.org/stable/c/720554c04acba80018ded069d3e0984bebaee891",
        "https://git.kernel.org/stable/c/84d5727cef8eb9c8a28210ad248f1c70b223b065",
        "https://git.kernel.org/stable/c/231542f4e43cf9837cb520664545e85fbe666b7b",
        "https://git.kernel.org/stable/c/2299822f3f466b5dcad2377bf63986199f881a6b"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
          "shortName": "Linux",
          "dateUpdated": "2026-10-26T06:56:27.943Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98900",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-cve",
  "document_id": 263358,
  "published_at": "2026-10-23T11:54:10.566+00:00"
}