CVE-2026-31617
Estado: ModificadaMedia (5.5)—
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.
Leer descripción completaMostrar menos
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.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.17%
- Percentil entre todas las CVEs puntuadas: 6
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- NVD-CWE-noinfo
- CWE-191
Referencias
- https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50
- https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7
- https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada
- https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135
- https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126
- https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1
- https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca
- https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb
- https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7
- https://access.redhat.com/security/cve/CVE-2026-31617
- https://bugzilla.redhat.com/show_bug.cgi?id=2461448
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31617.json
JSON original (NVD)
Mostrar
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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->ndp_size, the bounds check of:\n\tndp_index > (block_len - opts->ndp_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->dpe_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->ndp_size and\nblock_len - opts->dpe_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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