CVE-2026-97408: Bluetooth: L2CAP: validate connectionless PSM length

CVE-2026-97408: Bluetooth: L2CAP: validate connectionless PSM length

[Greg Kroah-Hartman]

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

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

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

Bluetooth: L2CAP: validate connectionless PSM length

Connectionless L2CAP frames carry a two-byte PSM at the start of the
payload.  l2cap_recv_frame() currently reads that PSM unconditionally
after validating only the outer L2CAP length.

A malformed connectionless frame with a zero- or one-byte payload can
therefore make the parser read beyond the advertised skb payload and use
tailroom bytes as part of the PSM.  A VHCI-backed QEMU reproducer
injected a one-byte connectionless payload and reached the unchecked
read.

Reject connectionless frames that cannot contain the PSM before reading
or pulling it.  This preserves all valid connectionless frames while
dropping only structurally incomplete packets.

The Linux kernel CVE team has assigned CVE-2026-97408 to this issue.


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

	Fixed in 6.12.111 with commit 3502ede8aed3c3ee1786d952a11054ac737d1a38
	Fixed in 6.18.53 with commit ae69dca122f6d6046a68cf40153e6e827c77ff5c
	Fixed in 7.2 with commit a40a5f922546b3bd7c094d882b29177db4f2abe0

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-2026-97408
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/3502ede8aed3c3ee1786d952a11054ac737d1a38
	https://git.kernel.org/stable/c/ae69dca122f6d6046a68cf40153e6e827c77ff5c
	https://git.kernel.org/stable/c/a40a5f922546b3bd7c094d882b29177db4f2abe0