# CVE-2026-43427: usb: class: cdc-wdm: fix reordering issue in read code path

Status: published. Published: 2026-05-08. Updated: 2026-11-06.

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

usb: class: cdc-wdm: fix reordering issue in read code path

Quoting the bug report:

Due to compiler optimization or CPU out-of-order execution, the
desc->length update can be reordered before the memmove. If this
happens, wdm_read() can see the new length and call copy_to_user() on
uninitialized memory. This also violates LKMM data race rules [1].

Fix it by using WRITE_ONCE and memory barriers.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 638328ca9c17ae6511ad62198c57bae32ffa3c91 (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 170e8daca24da6edb4be82ab01abf44e87af387b (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < c8fa96ed021923dae147bcd9f9205b8df7b82360 (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 4ee3062bf2c9a722afef429826e8607eaf3fc6a0 (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 276aef0fd2b92f41b920ac891c72cadeee957934 (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 67ed312124bb1b61858778ac0b985b48961c862a (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < e3c874b05901dc519054b5107d16620e6d2b5fea (affected, git); ≥ afba937e540c902c989cd516fd97ea0c8499bb27; < 8df672bfe3ec2268c2636584202755898e547173 (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.26 (affected); ≥ 0; < 2.6.26 (unaffected, semver); ≥ 5.10.253; ≤ 5.10.* (unaffected, semver); ≥ 5.15.203; ≤ 5.15.* (unaffected, semver); ≥ 6.1.167; ≤ 6.1.* (unaffected, semver); ≥ 6.6.130; ≤ 6.6.* (unaffected, semver); ≥ 6.12.78; ≤ 6.12.* (unaffected, semver); ≥ 6.18.19; ≤ 6.18.* (unaffected, semver); ≥ 6.19.9; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-06; percentile 2.82%

- 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/638328ca9c17ae6511ad62198c57bae32ffa3c91 (CNA: Linux)

- https://git.kernel.org/stable/c/170e8daca24da6edb4be82ab01abf44e87af387b (CNA: Linux)

- https://git.kernel.org/stable/c/c8fa96ed021923dae147bcd9f9205b8df7b82360 (CNA: Linux)

- https://git.kernel.org/stable/c/4ee3062bf2c9a722afef429826e8607eaf3fc6a0 (CNA: Linux)

- https://git.kernel.org/stable/c/276aef0fd2b92f41b920ac891c72cadeee957934 (CNA: Linux)

- https://git.kernel.org/stable/c/67ed312124bb1b61858778ac0b985b48961c862a (CNA: Linux)

- https://git.kernel.org/stable/c/e3c874b05901dc519054b5107d16620e6d2b5fea (CNA: Linux)

- https://git.kernel.org/stable/c/8df672bfe3ec2268c2636584202755898e547173 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-43427; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-43427; retrieved 2026-11-06; source updated Not reported

Revision: 5e0c68643673916368797fe9e618f18592d61dc5066d57d58e9184699c542987

Canonical: https://y2.dev/cve/CVE-2026-43427

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