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

Vulnerability from cvelistv5 – Published: 2026-04-24 14:42 – Updated: 2026-10-15 01:17
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
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-191 - Integer Underflow (Wrap or Wraparound)
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 068a7f2749fff6462a0a908ec415b885fe430f50 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 1425655c2870054c3ab4712e2b6dbdd331597ada (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 0f156bb5334e588034ca68ac2ee92b23f66e56e7 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 8757a2593631443648218244b9788e193ae0fdc1 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 6762f8a95772265dd0c2ffe7f400493f3115b135 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < d58ba8f6546232f8414f396c189297dbee03f1a7 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 74908b0318d1df1188457040b8714ff4d4b68126 (git)
Affected: 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 , < 8f993d30b95dc9557a8a96ceca11abed674c8acb (git)
Affected: f7e0611e207d8908c4f2858e244370529a76dbf7 (git)
Affected: b88ad6e714284b33a47834f5f2a294c2b37c66aa (git)
Affected: 471b23586387a32857778c511be60ab31c98dcfd (git)
Affected: 4f529c4d1e436230d3af7c09a3239677a14d2b46 (git)
Affected: ae6a5394d9fbe118bc95cfe376d6a9d91d7547e8 (git)
Affected: 4.9.235 , < 4.10 (semver)
Affected: 4.14.196 , < 4.15 (semver)
Affected: 4.19.143 , < 4.20 (semver)
Affected: 5.4.62 , < 5.5 (semver)
Affected: 5.8.6 , < 5.9 (semver)
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Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 5.10.258 , ≤ 5.10.* (semver)
Unaffected: 5.15.209 , ≤ 5.15.* (semver)
Unaffected: 6.1.175 , ≤ 6.1.* (semver)
Unaffected: 6.6.136 , ≤ 6.6.* (semver)
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)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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Red Hat Red Hat Enterprise Linux 10     cpe:/o:redhat:enterprise_linux:10
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Red Hat Red Hat Enterprise Linux 6     cpe:/o:redhat:enterprise_linux:6
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Red Hat Red Hat Enterprise Linux 7     cpe:/o:redhat:enterprise_linux:7
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Red Hat Red Hat Enterprise Linux 8     cpe:/o:redhat:enterprise_linux:8
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Red Hat Red Hat Enterprise Linux 9     cpe:/o:redhat:enterprise_linux:9
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Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
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    "dateReserved": "2026-03-09T15:48:24.123Z",
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      "product_status:known_affected": "3",
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        "descriptions": [
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            "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."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nusb: gadget: f_ncm: validar la longitud m\u00ednima de bloque (block_len) en ncm_unwrap_ntb()\n\nLa block_len le\u00edda del encabezado NTB proporcionado por el host se verifica contra ntb_max pero no tiene un l\u00edmite inferior. Cuando block_len es menor que opts  -\u003e  ndp_size, la verificaci\u00f3n de l\u00edmites de:\nndp_index \u003e (block_len - opts  -\u003e  ndp_size)\nse desbordar\u00e1 por debajo, produciendo un valor sin signo enorme que ndp_index nunca puede exceder, anulando la verificaci\u00f3n por completo.\n\nEl mismo desbordamiento por debajo ocurre en las verificaciones del \u00edndice del datagrama contra block_len - opts  -\u003e  dpe_size. Con esas verificaciones neutralizadas, un host USB malicioso puede elegir ndp_index y desplazamientos de datagrama que apuntan m\u00e1s all\u00e1 de la transferencia real, y skb_put_data() copia memoria adyacente del kernel en el skb de red.\n\nSolucione esto rechazando las longitudes de bloque que no pueden contener al menos el encabezado NTB m\u00e1s un NDP. Esto har\u00e1 que block_len - opts  -\u003e  ndp_size y block_len - opts  -\u003e  dpe_size est\u00e9n ambos bien definidos.\n\nEl commit 8d2b1a1ec9f5 (\u2019CDC-NCM: avoid overflow in sanity checking\u2019) solucion\u00f3 una clase de problemas relacionados en el lado del host de NCM."
          }
        ],
        "id": "CVE-2026-31617",
        "lastModified": "2026-11-11T23:10:00.263",
        "metrics": {
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                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 5.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
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                "scope": "UNCHANGED",
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                "value": "CWE-191"
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      "current_release_date": "2026-11-07T04:19:19+00:00",
      "cve": "CVE-2026-31617",
      "id": "CVE-2026-31617",
      "initial_release_date": "2026-04-24T00:00:00+00:00",
      "product_status:known_affected": "1",
      "product_status:known_not_affected": "199",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json",
      "version": "3"
    }
  }
}



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  • 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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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