CVE-2026-90021 usb: gadget: f_midi: initialize work in f_midi_alloc()
A missing initialization in the Linux kernel USB MIDI gadget driver can cause a null pointer dereference and system crash when the device is freed without being bound.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90021?
CVE-2026-90021 is a vulnerability in Linux, published on 16 Sep 2026. 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:
usb: gadget: f_midi: initialize work in f_midi_alloc()
f_midi_alloc initializes free_ref to 1 and it can only be incremented when a sound card is registered via f_midi_register_card(). f_midi_register_card() is only called in f_midi_bind() which actually performs INIT_WORK. If f_midi_bind() is never run, work is not initialized and the if condition in f_midi_free becomes true, this results in a warning later in __flush_work as work->func = 0. Fix this by moving INIT_WORK from f_midi_bind() to f_midi_alloc().
Which versions are affected by CVE-2026-90021?
How do I fix CVE-2026-90021?
Apply the vendor's patch.
Is CVE-2026-90021 being exploited?
There is no known exploitation of CVE-2026-90021 in the wild and no public exploit code.
Sources
Also known as AZL-101144, BELL-CVE-2026-90021, DEBIAN-CVE-2026-90021, GHSA-9v89-j77v-qgfm, UBUNTU-CVE-2026-90021.