CVE-2026-63896 (GCVE-0-2026-63896)
Vulnerability from cvelistv5
Published
2026-07-19 14:55
Modified
2026-07-19 14:55
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling The WebUSB GET_URL handler in composite_setup() narrows landing_page_length to fit the host-supplied wLength using landing_page_length = w_length - WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset; If wLength is smaller than WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH the unsigned subtraction wraps, and the subsequent memcpy(url_descriptor->URL, cdev->landing_page + landing_page_offset, landing_page_length - landing_page_offset); ends up copying close to UINT_MAX bytes from cdev->landing_page into cdev->req->buf. KASAN reports a slab-out-of-bounds in composite_setup on the kmalloc-2k gadget_info allocation, and FORTIFY_SOURCE traps the memcpy as a 4294967293-byte field-spanning write into url_descriptor->URL (size 252). A USB host can reach this from a single SETUP packet against any gadget that has webusb/use=1 and a landingPage configured. Handle the small-wLength case before the math: when the host requested fewer bytes than the URL descriptor header, only the header is meaningful and no URL bytes need to be copied. Setting landing_page_length to landing_page_offset makes the existing memcpy a no-op and leaves the descriptor returned to the host unchanged for all larger wLength values.
References
Impacted products
Vendor Product Version
Linux Linux Version: 93c473948c588978cd55d9a3adad8b3e8057aa21
Version: 93c473948c588978cd55d9a3adad8b3e8057aa21
Version: 93c473948c588978cd55d9a3adad8b3e8057aa21
Version: 93c473948c588978cd55d9a3adad8b3e8057aa21
Version: 93c473948c588978cd55d9a3adad8b3e8057aa21
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/composite.c"
          ],
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        {
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          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/composite.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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              "version": "6.3"
            },
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              "version": "0",
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              "version": "6.6.143",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: composite: fix integer underflow in WebUSB GET_URL handling\n\nThe WebUSB GET_URL handler in composite_setup() narrows\nlanding_page_length to fit the host-supplied wLength using\n\n\tlanding_page_length = w_length\n\t\t- WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset;\n\nIf wLength is smaller than WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH the\nunsigned subtraction wraps, and the subsequent\n\n\tmemcpy(url_descriptor-\u003eURL,\n\t       cdev-\u003elanding_page + landing_page_offset,\n\t       landing_page_length - landing_page_offset);\n\nends up copying close to UINT_MAX bytes from cdev-\u003elanding_page into\ncdev-\u003ereq-\u003ebuf.  KASAN reports a slab-out-of-bounds in composite_setup\non the kmalloc-2k gadget_info allocation, and FORTIFY_SOURCE traps the\nmemcpy as a 4294967293-byte field-spanning write into\nurl_descriptor-\u003eURL (size 252).\n\nA USB host can reach this from a single SETUP packet against any\ngadget that has webusb/use=1 and a landingPage configured.\n\nHandle the small-wLength case before the math: when the host requested\nfewer bytes than the URL descriptor header, only the header is\nmeaningful and no URL bytes need to be copied.  Setting\nlanding_page_length to landing_page_offset makes the existing memcpy a\nno-op and leaves the descriptor returned to the host unchanged for all\nlarger wLength values."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-19T14:55:06.152Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/046870ff6b6f7b743c953c061043a9b30700d491"
        },
        {
          "url": "https://git.kernel.org/stable/c/f5869dfaa89854dcf34121036294d42d6c7acb8f"
        },
        {
          "url": "https://git.kernel.org/stable/c/f8f5a8f48c7cae3fac85e04b593bd47939f9725f"
        },
        {
          "url": "https://git.kernel.org/stable/c/a20f0ccf45708af6e063c7234c215d364b00de25"
        },
        {
          "url": "https://git.kernel.org/stable/c/6c5dbc104dadd79fc2923497c20bae759a18758c"
        }
      ],
      "title": "usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63896",
    "datePublished": "2026-07-19T14:55:06.152Z",
    "dateReserved": "2026-07-19T07:54:57.019Z",
    "dateUpdated": "2026-07-19T14:55:06.152Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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