CVE-2026-89736: usb: gadget: u_audio: Fix use-after-free on sound card disconnect

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-11 · updated 2026-10-19

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.

Affected products

Linux kernel: from 5.10.177 before 5.10.270; from 5.15.105 before 5.15.221; from 6.1.22 before 6.1.188; from 4.14.312 before 4.15; from 4.19.280 before 4.20; from 5.4.240 before 5.5 — fixed in 4.15, 4.20, 5.10.270, 5.15.221, 5.5, 6.1.188

How to fix

Upgrade to a fixed version: Linux kernel 4.15, 4.20, 5.10.270, 5.15.221. Check the vendor advisory for mitigations.

References

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