GHSA-V24G-WPQ8-CWQX

Vulnerability from github – Published: 2026-04-24 15:32 – Updated: 2026-06-30 03:36
VLAI
Details

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
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-31617"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-191"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-24T15:16:40Z",
    "severity": "MODERATE"
  },
  "details": "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.",
  "id": "GHSA-v24g-wpq8-cwqx",
  "modified": "2026-06-30T03:36:23Z",
  "published": "2026-04-24T15:32:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31617"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-31617"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461448"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7"
    },
    {
      "type": "WEB",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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