CVE-2026-74540: Bluetooth: L2CAP: fix UAF in l2cap_le_connect_rsp

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

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

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

Bluetooth: L2CAP: fix UAF in l2cap_le_connect_rsp

l2cap_le_connect_rsp() obtains a channel via
__l2cap_get_chan_by_ident() but neither holds a reference nor uses
l2cap_chan_hold_unless_zero() before locking and operating on it.
A concurrent l2cap_chan_del() triggered by a remote disconnect can
free the channel between the lookup and l2cap_chan_lock(), causing
a use-after-free.

The BR/EDR counterpart l2cap_connect_rsp() and the sibling handler
l2cap_le_command_rej() already use l2cap_chan_hold_unless_zero()
to safely hold a reference, but l2cap_le_connect_rsp() was left
unprotected.

Fix by adding l2cap_chan_hold_unless_zero() after the ident lookup
and l2cap_chan_put() on the exit path, consistent with other L2CAP
response handlers.

The Linux kernel CVE team has assigned CVE-2026-74540 to this issue.


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

	Issue introduced in 3.14 with commit f1496dee9cbde2a62821f4441dadb0d3360f60c3 and fixed in 6.6.151 with commit fd4c1e301bdec60a40728ea37de531cbccda501a
	Issue introduced in 3.14 with commit f1496dee9cbde2a62821f4441dadb0d3360f60c3 and fixed in 6.12.103 with commit 522b730c62c53a1981604fd73524697fd347830d
	Issue introduced in 3.14 with commit f1496dee9cbde2a62821f4441dadb0d3360f60c3 and fixed in 6.18.44 with commit 58e3c5289ad230a7e24ae4b0c7b43f5ee6e32136
	Issue introduced in 3.14 with commit f1496dee9cbde2a62821f4441dadb0d3360f60c3 and fixed in 7.1.8 with commit 09f447accc2570751e7d17f0dc0788b40d3edade
	Issue introduced in 3.14 with commit f1496dee9cbde2a62821f4441dadb0d3360f60c3 and fixed in 7.2-rc6 with commit c4740e7f23ff9a8210198d8b4703259e21b9f69d

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-2026-74540
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:
	net/bluetooth/l2cap_core.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/fd4c1e301bdec60a40728ea37de531cbccda501a
	https://git.kernel.org/stable/c/522b730c62c53a1981604fd73524697fd347830d
	https://git.kernel.org/stable/c/58e3c5289ad230a7e24ae4b0c7b43f5ee6e32136
	https://git.kernel.org/stable/c/09f447accc2570751e7d17f0dc0788b40d3edade
	https://git.kernel.org/stable/c/c4740e7f23ff9a8210198d8b4703259e21b9f69d