linux-cve-announce - CVE-2026-23009: xhci: sideband: don't dereference freed ring when removing sideband endpoint

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Message-ID: <2026012537-CVE-2026-23009-7209@gregkh>
Date: Sun, 25 Jan 2026 15:36:45 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23009: xhci: sideband: don't dereference freed ring when removing sideband endpoint

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

xhci: sideband: don't dereference freed ring when removing sideband endpoint

xhci_sideband_remove_endpoint() incorrecly assumes that the endpoint is
running and has a valid transfer ring.

Lianqin reported a crash during suspend/wake-up stress testing, and
found the cause to be dereferencing a non-existing transfer ring
'ep->ring' during xhci_sideband_remove_endpoint().

The endpoint and its ring may be in unknown state if this function
is called after xHCI was reinitialized in resume (lost power), or if
device is being re-enumerated, disconnected or endpoint already dropped.

Fix this by both removing unnecessary ring access, and by checking
ep->ring exists before dereferencing it. Also make sure endpoint is
running before attempting to stop it.

Remove the xhci_initialize_ring_info() call during sideband endpoint
removal as is it only initializes ring structure enqueue, dequeue and
cycle state values to their starting values without changing actual
hardware enqueue, dequeue and cycle state. Leaving them out of sync
is worse than leaving it as it is. The endpoint will get freed in after
this in most usecases.

If the (audio) class driver want's to reuse the endpoint after offload
then it is up to the class driver to ensure endpoint is properly set up.

The Linux kernel CVE team has assigned CVE-2026-23009 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit de66754e9f8029f8ae955a588959b99cab56b506 and fixed in 6.18.7 with commit 34f6634dba87ef72b3c3a3a524be663adef7ab42
	Issue introduced in 6.16 with commit de66754e9f8029f8ae955a588959b99cab56b506 and fixed in 6.19-rc6 with commit dd83dc1249737b837ac5d57c81f2b0977c613d9f

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-2026-23009
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/host/xhci-sideband.c
	drivers/usb/host/xhci.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/34f6634dba87ef72b3c3a3a524be663adef7ab42
	https://git.kernel.org/stable/c/dd83dc1249737b837ac5d57c81f2b0977c613d9f