CVE-2026-72333: Bluetooth: L2CAP: fix tx ident leak for commands without a response

CVE-2026-72333: Bluetooth: L2CAP: fix tx ident leak for commands without a response

[Greg Kroah-Hartman]

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

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

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

Bluetooth: L2CAP: fix tx ident leak for commands without a response

Commit 6c3ea155e5ee ("Bluetooth: L2CAP: Fix not tracking outstanding
TX ident") changed ident allocation to use an IDA, releasing idents in
l2cap_put_ident() when the matching response command is received.

But identifiers allocated for commands that have no response defined
are never released. In particular L2CAP_LE_CREDITS is sent repeatedly for
the lifetime of an LE CoC channel, so a peer streaming data to the
host exhausts the 1-255 ident range after 254 credit packets. From
then on l2cap_get_ident() fails:

    kernel: Bluetooth: Unable to allocate ident: -28

and every subsequent L2CAP_LE_CREDITS packet is sent with ident 0,
which is invalid (Core Spec, Vol 3, Part A, Section 4: "Signaling
identifier 0x00 is an invalid identifier and shall never be used in
any command"). Remote stacks that validate the ident drop these
commands, never receive new credits, and the channel stalls
permanently. With default socket buffers this happens after roughly 0.5 MB
of received data (the exact amount depends on the socket receive buffer):

  < ACL Data TX: Handle 2048 flags 0x00 dlen 12
        LE L2CAP: LE Flow Control Credit (0x16) ident 0 len 4
          Source CID: 64
          Credits: 1

Release the ident immediately after sending L2CAP_LE_CREDITS since no
response will ever release it. Use a local variable instead of
chan->ident so that an ident that an EXT_FLOWCTL channel may be waiting on
(e.g. a pending reconfigure) is not overwritten by a credit packet.

Also add the missing L2CAP_LE_CONN_RSP case to l2cap_put_ident() so
idents allocated for outgoing L2CAP_LE_CONN_REQ commands are released
when the response arrives.

The Linux kernel CVE team has assigned CVE-2026-72333 to this issue.


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

	Issue introduced in 6.18.21 with commit ea6cf86167b3972caa68972d2a1ad43ecbbb8331 and fixed in 6.18.40 with commit 0c602cb8f148a36bfb39c25ade400bdadc023c4f
	Issue introduced in 7.0 with commit 6c3ea155e5ee3e56606233acde8309afda66d483 and fixed in 7.1.5 with commit d0a2b0c81f112540a337cde1c20251bf05ddf1da
	Issue introduced in 7.0 with commit 6c3ea155e5ee3e56606233acde8309afda66d483 and fixed in 7.2-rc3 with commit 6e1930ece855a4c256f1c7e6632d634cfb9888b5
	Issue introduced in 5.10.261 with commit ed97bb2cf96684ee646be6f37e4c4835f9d30caa
	Issue introduced in 5.15.212 with commit 84bc3197f7d87c5b89c156e853d0561a9154eceb
	Issue introduced in 6.19.11 with commit 8c1cdbc1bacc0cf9c27c3ebda11a81c3dcd01630

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-2026-72333
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/b8a32a5fc915b024c60f18d51b6cffd2bd64d4a6
	https://git.kernel.org/stable/c/bd1e01170341291292fd4c46b5f6949da282ca6c
	https://git.kernel.org/stable/c/0c602cb8f148a36bfb39c25ade400bdadc023c4f
	https://git.kernel.org/stable/c/d0a2b0c81f112540a337cde1c20251bf05ddf1da
	https://git.kernel.org/stable/c/6e1930ece855a4c256f1c7e6632d634cfb9888b5