# CVE-2026-64427: HID: logitech-dj: Fix maxfield check in DJ short report validation

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-07-25 · Updated: 2026-08-19

## Affected

- Linux: version range not reported
- Linux: 7.1

## Description

In the Linux kernel, the following vulnerability has been resolved: HID: logitech-dj: Fix maxfield check in DJ short report validation Commit b6a57912854e ("HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT related user initiated OOB write") added validation for the DJ short output report, but the error path dereferences rep->field[0] even when rep->maxfield is zero. Commit 8b9a097eb2fc ("HID: logitech-dj: fix wrong detection of bad DJ_SHORT output report") made the check conditional on rep being present, but a crafted descriptor can still create report ID 0x20 with only padding output items. hid-core registers the report, ignores the padding field, and leaves rep->maxfield as zero. In that case the validation enters the rep->maxfield < 1 branch and then dereferences rep->field[0]->report_count while printing the error message, causing a NULL pointer dereference during probe. This is reproducible with uhid by emulating a Logitech receiver with a padding-only DJ short output report: BUG: KASAN: null-ptr-deref in logi_dj_probe+0xb1/0x754 [hid_logitech_dj] Read of size 4 at addr 0000000000000028 by task kworker/4:1/129 ... Call Trace: logi_dj_probe+0xb1/0x754 [hid_logitech_dj] hid_device_probe+0x329/0x3f0 [hid] really_probe+0x162/0x570 __device_attach+0x137/0x2c0 bus_probe_device+0x38/0xc0 device_add+0xa56/0xce0 hid_add_device+0x19c/0x280 [hid] uhid_device_add_worker+0x2c/0xb0 [uhid] Reject the zero-field report before printing the field report_count.

## What to do

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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f3790a6af9c7f47d454225cab9dc145270e48f62
- https://git.kernel.org/stable/c/1215febd644c3e16f77e0f1799d89544dd57a754
- https://git.kernel.org/stable/c/6f7f22a8d244c2e586b8eb61c7585784b62aea01
- https://git.kernel.org/stable/c/95b3f23d632490b5eb285b9fcf7284f2ac8f9872
- https://git.kernel.org/stable/c/80c1e18473f63fd7c6a2bc9ad6f3d0a6cc4fb500
- https://git.kernel.org/stable/c/2b70bebc709489d29a31ac2935aeffb8d5228395
- https://git.kernel.org/stable/c/7a89ad762fad53d56b7002d7ffc923a4b7f4006f
- https://git.kernel.org/stable/c/590cc4d782487632a52f37c2171bee1eeea29627

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