From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89736: usb: gadget: u_audio: Fix use-after-free on sound card disconnect
Date: Fri, 11 Sep 2026 21:47:05 +0200 [thread overview]
Message-ID: <2026091103-CVE-2026-89736-b446@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@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.
The Linux kernel CVE team has assigned CVE-2026-89736 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.3 with commit 6c67ed9ad9b83e453e808f9b31a931a20a25629b and fixed in 6.12.109 with commit c74ff0b1a0fca53d3ac185873c87d6a719b30a47
Issue introduced in 6.3 with commit 6c67ed9ad9b83e453e808f9b31a931a20a25629b and fixed in 6.18.50 with commit 4e747c864a88537e18b1ffc19a1954c9686bb8e1
Issue introduced in 6.3 with commit 6c67ed9ad9b83e453e808f9b31a931a20a25629b and fixed in 7.2.4 with commit 79a92896e2bb9471550c56fc23d8d93592f04c27
Issue introduced in 6.3 with commit 6c67ed9ad9b83e453e808f9b31a931a20a25629b and fixed in 7.3-rc1 with commit 858965947081d10d41d9a1010a540d3d5eea958b
Issue introduced in 4.14.312 with commit 3e016ef2e72da93a2ea7afbb45de1b481b44d761
Issue introduced in 4.19.280 with commit 3256e152b645fc1e788ba44c2d8ced690113e3e6
Issue introduced in 5.4.240 with commit 0eda2004f38d95ef5715d62be884cd344260535b
Issue introduced in 5.10.177 with commit 33f341c1fc60e172a3515c51bdabee11e83d1ee9
Issue introduced in 5.15.105 with commit b131989797f7287d7fdadb2bababc05a15d44750
Issue introduced in 6.1.22 with commit 3bc7324e4911351e39c54a62e6ca46321cb10faf
Issue introduced in 6.2.9 with commit 43ca70753dfffd517d2af126da28690f8f615605
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-89736
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
drivers/usb/gadget/function/u_audio.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/c74ff0b1a0fca53d3ac185873c87d6a719b30a47
https://git.kernel.org/stable/c/4e747c864a88537e18b1ffc19a1954c9686bb8e1
https://git.kernel.org/stable/c/79a92896e2bb9471550c56fc23d8d93592f04c27
https://git.kernel.org/stable/c/858965947081d10d41d9a1010a540d3d5eea958b
reply other threads:[~2026-09-11 20:07 UTC|newest]
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