CVE-2026-31617 (GCVE-0-2026-31617)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:42 – Updated: 2026-04-24 14:42
VLAI?
Title
usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb() The block_len read from the host-supplied NTB header is checked against ntb_max but has no lower bound. When block_len is smaller than opts->ndp_size, the bounds check of: ndp_index > (block_len - opts->ndp_size) will underflow producing a huge unsigned value that ndp_index can never exceed, defeating the check entirely. The same underflow occurs in the datagram index checks against block_len - opts->dpe_size. With those checks neutered, a malicious USB host can choose ndp_index and datagram offsets that point past the actual transfer, and the skb_put_data() copies adjacent kernel memory into the network skb. Fix this by rejecting block lengths that cannot hold at least the NTB header plus one NDP. This will make block_len - opts->ndp_size and block_len - opts->dpe_size both well-defined. Commit 8d2b1a1ec9f5 ("CDC-NCM: avoid overflow in sanity checking") fixed a related class of issues on the host side of NCM.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8757a2593631443648218244b9788e193ae0fdc1 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6762f8a95772265dd0c2ffe7f400493f3115b135 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d58ba8f6546232f8414f396c189297dbee03f1a7 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 74908b0318d1df1188457040b8714ff4d4b68126 (git)
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    Linux Linux Unaffected: 6.12.83 , ≤ 6.12.* (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0.1 , ≤ 7.0.* (semver)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/function/f_ncm.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "6.12.83",
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              "versionType": "semver"
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()\n\nThe block_len read from the host-supplied NTB header is checked against\nntb_max but has no lower bound. When block_len is smaller than\nopts-\u003endp_size, the bounds check of:\n\tndp_index \u003e (block_len - opts-\u003endp_size)\nwill underflow producing a huge unsigned value that ndp_index can never\nexceed, defeating the check entirely.\n\nThe same underflow occurs in the datagram index checks against block_len\n- opts-\u003edpe_size.  With those checks neutered, a malicious USB host can\nchoose ndp_index and datagram offsets that point past the actual\ntransfer, and the skb_put_data() copies adjacent kernel memory into the\nnetwork skb.\n\nFix this by rejecting block lengths that cannot hold at least the NTB\nheader plus one NDP.  This will make block_len - opts-\u003endp_size and\nblock_len - opts-\u003edpe_size both well-defined.\n\nCommit 8d2b1a1ec9f5 (\"CDC-NCM: avoid overflow in sanity checking\") fixed\na related class of issues on the host side of NCM."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-24T14:42:36.191Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1"
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        },
        {
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        },
        {
          "url": "https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126"
        }
      ],
      "title": "usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()",
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        "engine": "bippy-1.2.0"
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  },
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31617",
    "datePublished": "2026-04-24T14:42:36.191Z",
    "dateReserved": "2026-03-09T15:48:24.123Z",
    "dateUpdated": "2026-04-24T14:42:36.191Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-31617",
      "date": "2026-04-25",
      "epss": "0.00018",
      "percentile": "0.04621"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31617\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-24T15:16:40.973\",\"lastModified\":\"2026-04-24T17:51:40.810\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nusb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()\\n\\nThe block_len read from the host-supplied NTB header is checked against\\nntb_max but has no lower bound. When block_len is smaller than\\nopts-\u003endp_size, the bounds check of:\\n\\tndp_index \u003e (block_len - opts-\u003endp_size)\\nwill underflow producing a huge unsigned value that ndp_index can never\\nexceed, defeating the check entirely.\\n\\nThe same underflow occurs in the datagram index checks against block_len\\n- opts-\u003edpe_size.  With those checks neutered, a malicious USB host can\\nchoose ndp_index and datagram offsets that point past the actual\\ntransfer, and the skb_put_data() copies adjacent kernel memory into the\\nnetwork skb.\\n\\nFix this by rejecting block lengths that cannot hold at least the NTB\\nheader plus one NDP.  This will make block_len - opts-\u003endp_size and\\nblock_len - opts-\u003edpe_size both well-defined.\\n\\nCommit 8d2b1a1ec9f5 (\\\"CDC-NCM: avoid overflow in sanity checking\\\") fixed\\na related class of issues on the host side of NCM.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • 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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