# CVE-2026-89736

## Summary

- **CVE ID:** CVE-2026-89736
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 14, 2026

## 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 — Linux (6c67ed9ad9b83e453e808f9b31a931a20a25629b)
- Linux — Linux (3e016ef2e72da93a2ea7afbb45de1b481b44d761)
- Linux — Linux (3256e152b645fc1e788ba44c2d8ced690113e3e6)
- Linux — Linux (0eda2004f38d95ef5715d62be884cd344260535b)
- Linux — Linux (33f341c1fc60e172a3515c51bdabee11e83d1ee9)
- Linux — Linux (b131989797f7287d7fdadb2bababc05a15d44750)
- Linux — Linux (3bc7324e4911351e39c54a62e6ca46321cb10faf)
- Linux — Linux (43ca70753dfffd517d2af126da28690f8f615605)
- Linux — Linux (4.14.312)
- Linux — Linux (4.19.280)
- Linux — Linux (5.4.240)
- Linux — Linux (5.10.177)
- Linux — Linux (5.15.105)
- Linux — Linux (6.1.22)
- Linux — Linux (6.2.9)
- Linux — Linux (6.3)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (5.10.270)
- Linux — Linux (5.15.221)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/c74ff0b1a0fca53d3ac185873c87d6a719b30a47)
- [CNA](https://git.kernel.org/stable/c/4e747c864a88537e18b1ffc19a1954c9686bb8e1)
- [CNA](https://git.kernel.org/stable/c/79a92896e2bb9471550c56fc23d8d93592f04c27)
- [CNA](https://git.kernel.org/stable/c/858965947081d10d41d9a1010a540d3d5eea958b)
- [CNA](https://git.kernel.org/stable/c/a7ecd1a04f4f485d7be6443d0f0b2c61a800cb82)
- [CNA](https://git.kernel.org/stable/c/f983793f03148b097977f200298db215cd2d4438)
- [CNA](https://git.kernel.org/stable/c/6f46762196f04464e1050a9ee94e72b917db9010)
- [CNA](https://git.kernel.org/stable/c/891a8d11f4d5eb50b2ce7570f4f98204a7a57493)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.13%
- **EPSS Percentile:** 2.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._