# CVE-2025-21948: HID: appleir: Fix potential NULL dereference at raw event handle
> A NULL pointer dereference in the Linux kernel's Apple IR HID driver allows local attackers to cause a system crash via crafted USB input events.
- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Apr 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-59946, AZL-59960, BELL-CVE-2025-21948, DEBIAN-CVE-2025-21948, GHSA-jxxv-c48x-753p, ROOT-OS-UBUNTU-2404-CVE-2025-21948, UBUNTU-CVE-2025-21948
## What is CVE-2025-21948?
CVE-2025-21948 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
### Official description
In the Linux kernel, the following vulnerability has been resolved:
HID: appleir: Fix potential NULL dereference at raw event handle
Syzkaller reports a NULL pointer dereference issue in input_event().
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in is_event_supported drivers/input/input.c:67 [inline]
BUG: KASAN: null-ptr-deref in input_event+0x42/0xa0 drivers/input/input.c:395
Read of size 8 at addr 0000000000000028 by task syz-executor199/2949
CPU: 0 UID: 0 PID: 2949 Comm: syz-executor199 Not tainted 6.13.0-rc4-syzkaller-00076-gf097a36ef88d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
kasan_report+0xd9/0x110 mm/kasan/report.c:602
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:68 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
is_event_supported drivers/input/input.c:67 [inline]
input_event+0x42/0xa0 drivers/input/input.c:395
input_report_key include/linux/input.h:439 [inline]
key_down drivers/hid/hid-appleir.c:159 [inline]
appleir_raw_event+0x3e5/0x5e0 drivers/hid/hid-appleir.c:232
__hid_input_report.constprop.0+0x312/0x440 drivers/hid/hid-core.c:2111
hid_ctrl+0x49f/0x550 drivers/hid/usbhid/hid-core.c:484
__usb_hcd_giveback_urb+0x389/0x6e0 drivers/usb/core/hcd.c:1650
usb_hcd_giveback_urb+0x396/0x450 drivers/usb/core/hcd.c:1734
dummy_timer+0x17f7/0x3960 drivers/usb/gadget/udc/dummy_hcd.c:1993
__run_hrtimer kernel/time/hrtimer.c:1739 [inline]
__hrtimer_run_queues+0x20a/0xae0 kernel/time/hrtimer.c:1803
hrtimer_run_softirq+0x17d/0x350 kernel/time/hrtimer.c:1820
handle_softirqs+0x206/0x8d0 kernel/softirq.c:561
__do_softirq kernel/softirq.c:595 [inline]
invoke_softirq kernel/softirq.c:435 [inline]
__irq_exit_rcu+0xfa/0x160 kernel/softirq.c:662
irq_exit_rcu+0x9/0x30 kernel/softirq.c:678
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
sysvec_apic_timer_interrupt+0x90/0xb0 arch/x86/kernel/apic/apic.c:1049
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
__mod_timer+0x8f6/0xdc0 kernel/time/timer.c:1185
add_timer+0x62/0x90 kernel/time/timer.c:1295
schedule_timeout+0x11f/0x280 kernel/time/sleep_timeout.c:98
usbhid_wait_io+0x1c7/0x380 drivers/hid/usbhid/hid-core.c:645
usbhid_init_reports+0x19f/0x390 drivers/hid/usbhid/hid-core.c:784
hiddev_ioctl+0x1133/0x15b0 drivers/hid/usbhid/hiddev.c:794
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl fs/ioctl.c:892 [inline]
__x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
This happens due to the malformed report items sent by the emulated device
which results in a report, that has no fields, being added to the report list.
Due to this appleir_input_configured() is never called, hidinput_connect()
fails which results in the HID_CLAIMED_INPUT flag is not being set. However,
it does not make appleir_probe() fail and lets the event callback to be
called without the associated input device.
Thus, add a check for the HID_CLAIMED_INPUT flag and leave the event hook
early if the driver didn't claim any input_dev for some reason. Moreover,
some other hid drivers accessing input_dev in their event callbacks do have
similar checks, too.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Weakness: CWE-476 (NULL Pointer Dereference)
## Which versions are affected by CVE-2025-21948?
It affects 1 product.
Products: Linux kernel.
## How do I fix CVE-2025-21948?
Apply the vendor's patch.
## Is CVE-2025-21948 being exploited?
There is no known exploitation of CVE-2025-21948 in the wild and no public exploit code.
## Other vulnerabilities in Linux kernel
- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)
## Fix prompt for AI coding agents
```text
Check this codebase for CVE-2025-21948 and fix it if it is affected.
What it is: CVE-2025-21948 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-21948 in the wild and no public exploit code.
Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2025-21948/ (Markdown: https://insights.sbomify.com/CVE-2025-21948/index.md)
```
## Sources
- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21948
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21948
- OSV: https://osv.dev/vulnerability/CVE-2025-21948
---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21948/
Summaries are generated and may contain mistakes; the official description above is the record.