CVE-2026-31617 (GCVE-0-2026-31617)
Vulnerability from cvelistv5
Published
2026-04-24 14:42
Modified
2026-08-06 12:08
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52
Version: f7e0611e207d8908c4f2858e244370529a76dbf7
Version: b88ad6e714284b33a47834f5f2a294c2b37c66aa
Version: 471b23586387a32857778c511be60ab31c98dcfd
Version: 4f529c4d1e436230d3af7c09a3239677a14d2b46
Version: ae6a5394d9fbe118bc95cfe376d6a9d91d7547e8
Version: 4.9.235   ≤
Version: 4.14.196   ≤
Version: 4.19.143   ≤
Version: 5.4.62   ≤
Version: 5.8.6   ≤
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          "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."
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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": "2026-08-06T12:08:53.324Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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