CVE-2026-31617
Modified
Modified - Updated After Analysis
BaseFortify
Vulnerability report for CVE-2026-31617, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-04-24
Last updated on: 2026-06-30
Assigner: kernel.org
Description
Description
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 Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | From 6.13 (inc) to 6.18.24 (exc) |
| linux | linux_kernel | From 6.19 (inc) to 6.19.14 (exc) |
| linux | linux_kernel | From 7.0 (inc) to 7.0.1 (exc) |
| linux | linux_kernel | From 6.12 (inc) to 6.12.83 (exc) |
| linux | linux_kernel | From 5.9 (inc) to 6.6.136 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-191 | The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. |
