CVE-2026-89736
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, the USB gadget u_audio driver has a use-after-free in g_audio_cleanup(). snd_card_free_when_closed() returns asynchronously while the snd_uac_chip structure is freed immediately, leaving ALSA control handles (kctls) open in userspace. Accessing these handles dereferences freed memory.
Risk Assessment
A local user can trigger memory corruption (UAF), potentially causing a system crash or privilege escalation. Systems using USB gadget audio are at risk.
Recommendation
Update the Linux kernel to a version containing the fix that registers a card->private_free callback and frees the uac structure only after all sound card references are released.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS