CVE-2026-89736 usb: gadget: u_audio: Fix use-after-free on sound card disconnect
A use-after-free in the Linux kernel USB audio gadget allows local attackers to cause memory corruption and potentially execute code or escalate privileges.
- 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
What is CVE-2026-89736?
CVE-2026-89736 is a high-severity use after free vulnerability in Linux, published on 11 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: u_audio: Fix use-after-free on sound card disconnect
g_audio_cleanup() invokes snd_card_free_when_closed() to initiate sound card teardown and immediately frees the underlying struct snd_uac_chip context. However, snd_card_free_when_closed() returns asynchronously while ALSA control elements (kctls) remain open in userspace.
When userspace control applications access or close these open file descriptors, kctl callbacks attempt to dereference kctl->private_data pointing to &uac->c_prm or &uac->p_prm within the freed uac structure, resulting in a use-after-free (UAF) memory corruption.
Fix this issue by deferring the destruction of struct snd_uac_chip until all references to the ALSA sound card are released. Register a custom card->private_free callback (u_audio_card_free) during g_audio_setup() that frees uac and its associated playback/capture request and ring buffers only when the sound card reference count drops to zero.
Which versions are affected by CVE-2026-89736?
How do I fix CVE-2026-89736?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89736 being exploited?
There is no known exploitation of CVE-2026-89736 in the wild and no public exploit code.
Sources
Also known as AZL-100683, BELL-CVE-2026-89736, DEBIAN-CVE-2026-89736, GHSA-hjw3-qcfv-9g4p, UBUNTU-CVE-2026-89736.