# CVE-2026-68368: usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb()

Status: published. Published: 2026-08-10. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb()

When unpacking host-supplied NTBs, ncm_unwrap_ntb() checks datagram length
against frame_max but does not verify that the datagram fits within the
declared block length. Additionally, when decoding multiple NTBs from a
single socket buffer, subsequent block lengths are not checked against the
actual remaining buffer data.

With these checks missing, a malicious USB host can specify datagram
offsets and lengths that point beyond the block, or supply secondary NTB
headers declaring lengths larger than the buffer. skb_put_data() then
copies adjacent kernel memory from skb_shared_info into the network skb.

Fix this by verifying that sufficient buffer space remains for the NTB
header before parsing, handling zero-length block declarations, ensuring
that block lengths never exceed the remaining buffer space, and verifying
that each datagram payload stays strictly within the block boundary.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < 35d15bbaec0557330e774ec31412ef508de6e0e0 (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < 6b2be489eaa6293e60549005d91f15ceb150510f (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < f87ed889f0f7417b8938c98d8833f559b755373c (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < fff1059d139ef798bab917990524faaf25854ca8 (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < 40c706a0224bde194667e3378c689b542fec4b44 (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < 41fd5f2fb0027d3773ae949e3247c2e0a2a7fe5c (affected, git); ≥ 2b74b0a04d3e9f9f08ff026e5663dce88ff94e52; < 1febec7e47cdcd01f43fb0211094e3010474666e (affected, git); f7e0611e207d8908c4f2858e244370529a76dbf7 (affected, git); b88ad6e714284b33a47834f5f2a294c2b37c66aa (affected, git); 471b23586387a32857778c511be60ab31c98dcfd (affected, git); 4f529c4d1e436230d3af7c09a3239677a14d2b46 (affected, git); ae6a5394d9fbe118bc95cfe376d6a9d91d7547e8 (affected, git); 5bdf93a2f5459f944b416b188178ca4a92fd206f (affected, git); ff3ba016263ee93a1c6209bf5ab1599de7ab1512 (affected, git); e7ca00f35d8a17af1ae19d529193ebc21bfda164 (affected, git); ≥ 4.9.235; < 4.10 (affected, semver); ≥ 4.14.196; < 4.15 (affected, semver); ≥ 4.19.143; < 4.20 (affected, semver); ≥ 5.4.62; < 5.5 (affected, semver); ≥ 5.8.6; < 5.9 (affected, semver); ≥ 4.14.328; < 4.15 (affected, semver); ≥ 4.19.297; < 4.20 (affected, semver); ≥ 5.4.259; < 5.5 (affected, semver). Source: CNA: Linux
- Linux / Linux: 5.9 (affected); ≥ 0; < 5.9 (unaffected, semver); ≥ 5.10.265; ≤ 5.10.* (unaffected, semver); ≥ 5.15.216; ≤ 5.15.* (unaffected, semver); ≥ 6.1.183; ≤ 6.1.* (unaffected, semver); ≥ 6.6.148; ≤ 6.6.* (unaffected, semver); ≥ 6.12.101; ≤ 6.12.* (unaffected, semver); ≥ 6.18.42; ≤ 6.18.* (unaffected, semver); ≥ 7.1.6; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.22% as of 2026-11-06; percentile 12.13%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/35d15bbaec0557330e774ec31412ef508de6e0e0 (CNA: Linux)

- https://git.kernel.org/stable/c/6b2be489eaa6293e60549005d91f15ceb150510f (CNA: Linux)

- https://git.kernel.org/stable/c/f87ed889f0f7417b8938c98d8833f559b755373c (CNA: Linux)

- https://git.kernel.org/stable/c/e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f (CNA: Linux)

- https://git.kernel.org/stable/c/fff1059d139ef798bab917990524faaf25854ca8 (CNA: Linux)

- https://git.kernel.org/stable/c/40c706a0224bde194667e3378c689b542fec4b44 (CNA: Linux)

- https://git.kernel.org/stable/c/41fd5f2fb0027d3773ae949e3247c2e0a2a7fe5c (CNA: Linux)

- https://git.kernel.org/stable/c/1febec7e47cdcd01f43fb0211094e3010474666e (CNA: Linux)

- https://git.kernel.org/stable/c/1febec7e47cdcd01f43fb0211094e3010474666e (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/35d15bbaec0557330e774ec31412ef508de6e0e0 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/40c706a0224bde194667e3378c689b542fec4b44 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/41fd5f2fb0027d3773ae949e3247c2e0a2a7fe5c (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/6b2be489eaa6293e60549005d91f15ceb150510f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/f87ed889f0f7417b8938c98d8833f559b755373c (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/fff1059d139ef798bab917990524faaf25854ca8 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-68368; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68368; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-68368; retrieved 2026-11-06; source updated Not reported

Revision: adaad003dc9586b4cf40ce2e5663132e4da15a2b82e644bab6bea991135d0142

Canonical: https://y2.dev/cve/CVE-2026-68368

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