CVE-2025-38557
Description
From CVE.org
In the Linux kernel, the following vulnerability has been resolved: HID: apple: validate feature-report field count to prevent NULL pointer dereference A malicious HID device with quirk APPLE_MAGIC_BACKLIGHT can trigger a NULL pointer dereference whilst the power feature-report is toggled and sent to the device in apple_magic_backlight_report_set(). The power feature-report is expected to have two data fields, but if the descriptor declares one field then accessing field[1] and dereferencing it in apple_magic_backlight_report_set() becomes invalid since field[1] will be NULL. An example of a minimal descriptor which can cause the crash is something like the following where the report with ID 3 (power report) only references a single 1-byte field. When hid core parses the descriptor it will encounter the final feature tag, allocate a hid_report (all members of field[] will be zeroed out), create field structure and populate it, increasing the maxfield to 1. The subsequent field[1] access and dereference causes the crash. Usage Page (Vendor Defined 0xFF00) Usage (0x0F) Collection (Application) Report ID (1) Usage (0x01) Logical Minimum (0) Logical Maximum (255) Report Size (8) Report Count (1) Feature (Data,Var,Abs) Usage (0x02) Logical Maximum (32767) Report Size (16) Report Count (1) Feature (Data,Var,Abs) Report ID (3) Usage (0x03) Logical Minimum (0) Logical Maximum (1) Report Size (8) Report Count (1) Feature (Data,Var,Abs) End Collection Here we see the KASAN splat when the kernel dereferences the NULL pointer and crashes: [ 15.164723] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP KASAN NOPTI [ 15.165691] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 15.165691] CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Not tainted 6.15.0 #31 PREEMPT(voluntary) [ 15.165691] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 [ 15.165691] RIP: 0010:apple_magic_backlight_report_set+0xbf/0x210 [ 15.165691] Call Trace: [ 15.165691] <TASK> [ 15.165691] apple_probe+0x571/0xa20 [ 15.165691] hid_device_probe+0x2e2/0x6f0 [ 15.165691] really_probe+0x1ca/0x5c0 [ 15.165691] __driver_probe_device+0x24f/0x310 [ 15.165691] driver_probe_device+0x4a/0xd0 [ 15.165691] __device_attach_driver+0x169/0x220 [ 15.165691] bus_for_each_drv+0x118/0x1b0 [ 15.165691] __device_attach+0x1d5/0x380 [ 15.165691] device_initial_probe+0x12/0x20 [ 15.165691] bus_probe_device+0x13d/0x180 [ 15.165691] device_add+0xd87/0x1510 [...] To fix this issue we should validate the number of fields that the backlight and power reports have and if they do not have the required number of fields then bail.
Statement
A malformed HID device advertising the APPLE_MAGIC_BACKLIGHT quirk can supply a power/brightness feature report with too few fields, causing a NULL pointer dereference in apple_magic_backlight_report_set() during probe. This is a local, physically-adjacent attack (malicious USB HID) that results in kernel crash (availability impact only); confidentiality and integrity are unaffected.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.6 | 5.5 | N/A |
| Attack Vector | Physical | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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