CVE-2026-89736

Received Received - Intake

Use-After-Free in Linux Kernel USB Gadget Audio Driver

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89736

EUVD

EUVD-2026-76648

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free (UAF) issue in the Linux kernel's USB gadget audio driver. When a sound card is disconnected, the cleanup function frees memory while userspace applications may still hold open file descriptors to ALSA control elements. These elements later try to access freed memory, causing memory corruption.

Detection Guidance

This vulnerability is specific to the Linux kernel's USB gadget audio driver and requires kernel-level inspection. Detection involves checking kernel logs for use-after-free errors related to ALSA sound card operations. Monitor dmesg for messages like 'use-after-free' or 'snd_card_free_when_closed' after disconnecting USB audio gadgets. No direct network detection commands are applicable.

Impact Analysis

This could lead to system crashes, data corruption, or potential privilege escalation if exploited. Users with USB audio gadgets may experience instability or security issues when disconnecting devices.

Mitigation Strategies

Apply the latest Linux kernel patches that include the fix for this issue. If patching is not immediately possible, avoid using USB audio gadgets until the patch is applied. Monitor kernel logs for related errors and restrict access to USB audio devices if feasible.

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