Medium 5.5Published Apr 24, 2026

CVE-2026-31617usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

Updated under an hour ago (Oct 28, 2026, 12:30 AM ET)

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Exploited in the last 30 days

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.

CVSS: 5.5 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-191
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 068a7f2749fff6462a0a908ec415b885fe430f50; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 1425655c2870054c3ab4712e2b6dbdd331597ada; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca; 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 builds before 0f156bb5334e588034ca68ac2ee92b23f66e56e7; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 8757a2593631443648218244b9788e193ae0fdc1; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 6762f8a95772265dd0c2ffe7f400493f3115b135; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before d58ba8f6546232f8414f396c189297dbee03f1a7; from 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 before 74908b0318d1df1188457040b8714ff4d4b68126; and 11 more ranges	CNA record
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux	10	CISA ADP
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name)	all versions	CISA ADP
linux linux_kernel linux:linux_kernel	from 5.9 before 6.6.136; from 6.12 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; from 7.0 before 7.0.1	NVD

References

References

https://git.kernel.org/stable/c/068a7f2749fff6462a0a908ec415b885fe430f50
https://git.kernel.org/stable/c/1425655c2870054c3ab4712e2b6dbdd331597ada
https://git.kernel.org/stable/c/8b3b7bd3c02f98634baaf36c7fc7ac915f6517ca
https://git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7	patch
https://git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1	patch
https://git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135	patch
https://git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7	patch
https://git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126	patch
https://git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb	patch
https://access.redhat.com/security/cve/CVE-2026-31617
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.