CVE-2026-68339: Bluetooth: btusb: validate Realtek vendor event length

From: Greg Kroah-Hartman <[email protected]>

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

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

Bluetooth: btusb: validate Realtek vendor event length

btusb_recv_event_realtek() reads the event code at data[0] and the Realtek
subevent code at data[2] before deciding whether to consume a vendor event
as a coredump.

For example, the two-byte event ff 00 contains a complete vendor-event
header declaring zero parameters. The old classifier still reads a
nonexistent third byte and can misclassify the event as a coredump if the
adjacent byte is 0x34.

Require the HCI event header and first parameter to be present before
inspecting the Realtek subevent code. Short events continue through the
normal HCI receive path, which owns their protocol validation.

The Linux kernel CVE team has assigned CVE-2026-68339 to this issue.


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

	Issue introduced in 6.6 with commit 044014ce85a17c0b7fab8e5df0925792010c29b2 and fixed in 6.6.148 with commit 8de58bfa26e028f99271dde5a92107cd07f5e063
	Issue introduced in 6.6 with commit 044014ce85a17c0b7fab8e5df0925792010c29b2 and fixed in 6.12.101 with commit 400267bab0f4076088e163e58cad2bb41c3cf5e7
	Issue introduced in 6.6 with commit 044014ce85a17c0b7fab8e5df0925792010c29b2 and fixed in 6.18.42 with commit 8881daaafadbe7fb2b7341d16a3949114409c90c
	Issue introduced in 6.6 with commit 044014ce85a17c0b7fab8e5df0925792010c29b2 and fixed in 7.1.6 with commit 24b0758193d70da47ef8b979153d2a181dbdf34e
	Issue introduced in 6.6 with commit 044014ce85a17c0b7fab8e5df0925792010c29b2 and fixed in 7.2-rc5 with commit df541cd485ff80a5ddc579d99687bc7506df9851

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-2026-68339
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/bluetooth/btusb.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/8de58bfa26e028f99271dde5a92107cd07f5e063
	https://git.kernel.org/stable/c/400267bab0f4076088e163e58cad2bb41c3cf5e7
	https://git.kernel.org/stable/c/8881daaafadbe7fb2b7341d16a3949114409c90c
	https://git.kernel.org/stable/c/24b0758193d70da47ef8b979153d2a181dbdf34e
	https://git.kernel.org/stable/c/df541cd485ff80a5ddc579d99687bc7506df9851