CVE-2026-80760: Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255

mgmt_hci_cmd_sync() checks that the message length agrees with params_len
but puts no upper bound on it. params_len is __le16 while the parameter
length in the HCI command header is a u8:

	struct hci_command_hdr {
		__le16	opcode;
		__u8	plen;
	} __packed;

hci_cmd_sync_alloc() assigns one to the other:

	hdr->plen = plen;

	if (plen)
		skb_put_data(skb, param, plen);

so a params_len of 256 leaves plen at 0 while all 256 bytes are still
appended. The frame handed to the driver then declares no parameters and
carries 256 of them. On a length framed transport such as H:4 the
controller takes the trailing bytes as the start of the next packet.

The mgmt socket MTU is HCI_MAX_FRAME_SIZE, so params_len can reach about
1KB this way. Commit 03f1700b9b4d ("Bluetooth: MGMT: reject malformed
HCI_CMD_SYNC commands") only made params_len agree with the message
length, a value that fits the message but not the header field is still
accepted.

Reject params_len that does not fit the header field.

The Linux kernel CVE team has assigned CVE-2026-80760 to this issue.


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

	Issue introduced in 6.13 with commit 827af4787e74e8df9e8e0677a69fbb15e0856d2f and fixed in 6.18.47 with commit b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
	Issue introduced in 6.13 with commit 827af4787e74e8df9e8e0677a69fbb15e0856d2f and fixed in 7.1.11 with commit 0bd0195ce25737cbdd0eabc54319ee0ddf3a0ad2
	Issue introduced in 6.13 with commit 827af4787e74e8df9e8e0677a69fbb15e0856d2f and fixed in 7.2.1 with commit 6e1c44878aa3ee7336efeaf01414b030b0a5c273
	Issue introduced in 6.13 with commit 827af4787e74e8df9e8e0677a69fbb15e0856d2f and fixed in 7.3-rc1 with commit 5d95286b6d6e8f1d304da7522bfa6860fc017e48

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-2026-80760
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/mgmt.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/b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
	https://git.kernel.org/stable/c/0bd0195ce25737cbdd0eabc54319ee0ddf3a0ad2
	https://git.kernel.org/stable/c/6e1c44878aa3ee7336efeaf01414b030b0a5c273
	https://git.kernel.org/stable/c/5d95286b6d6e8f1d304da7522bfa6860fc017e48