usb: gadget: f_ncm: validate minimum block_len in ncm_unwrap_ntb()

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Summary

CVECVE-2026-31617
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-24 15:16:40 UTC
Updated2026-04-28 17:27:20 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000180000 probability, percentile 0.048130000 (date 2026-04-27)

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 0f156bb5334e588034ca68ac2ee92b23f66e56e7 git Not specified
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 8757a2593631443648218244b9788e193ae0fdc1 git Not specified
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 6762f8a95772265dd0c2ffe7f400493f3115b135 git Not specified
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 d58ba8f6546232f8414f396c189297dbee03f1a7 git Not specified
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 74908b0318d1df1188457040b8714ff4d4b68126 git Not specified
CNA Linux Linux affected 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52 8f993d30b95dc9557a8a96ceca11abed674c8acb git Not specified
CNA Linux Linux affected f7e0611e207d8908c4f2858e244370529a76dbf7 git Not specified
CNA Linux Linux affected b88ad6e714284b33a47834f5f2a294c2b37c66aa git Not specified
CNA Linux Linux affected 471b23586387a32857778c511be60ab31c98dcfd git Not specified
CNA Linux Linux affected 4f529c4d1e436230d3af7c09a3239677a14d2b46 git Not specified
CNA Linux Linux affected ae6a5394d9fbe118bc95cfe376d6a9d91d7547e8 git Not specified
CNA Linux Linux affected 5.9 Not specified
CNA Linux Linux unaffected 5.9 semver Not specified
CNA Linux Linux unaffected 6.6.136 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.83 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.24 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.14 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0.1 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/0f156bb5334e588034ca68ac2ee92b23f66e56e7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8757a2593631443648218244b9788e193ae0fdc1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8f993d30b95dc9557a8a96ceca11abed674c8acb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/74908b0318d1df1188457040b8714ff4d4b68126 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/d58ba8f6546232f8414f396c189297dbee03f1a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/6762f8a95772265dd0c2ffe7f400493f3115b135 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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