CVE-2026-43023

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

Bluetooth: SCO: fix race conditions in sco_sock_connect()

sco_sock_connect() checks sk_state and sk_type without holding

the socket lock. Two concurrent connect() syscalls on the same

socket can both pass the check and enter sco_connect(), leading

to use-after-free.

The buggy scenario involves three participants and was confirmed

with additional logging instrumentation:

Thread A (connect): HCI disconnect: Thread B (connect):

sco_sock_connect(sk) sco_sock_connect(sk)

sk_state==BT_OPEN sk_state==BT_OPEN

(pass, no lock) (pass, no lock)

sco_connect(sk): sco_connect(sk):

hci_dev_lock hci_dev_lock

hci_connect_sco <- blocked

-> hcon1

sco_conn_add->conn1

lock_sock(sk)

sco_chan_add:

conn1->sk = sk

sk->conn = conn1

sk_state=BT_CONNECT

release_sock

hci_dev_unlock

hci_dev_lock

sco_conn_del:

lock_sock(sk)

sco_chan_del:

sk->conn=NULL

conn1->sk=NULL

sk_state=

BT_CLOSED

SOCK_ZAPPED

release_sock

hci_dev_unlock

(unblocked)

hci_connect_sco

-> hcon2

sco_conn_add

-> conn2

lock_sock(sk)

sco_chan_add:

sk->conn=conn2

sk_state=

BT_CONNECT

// zombie sk!

release_sock

hci_dev_unlock

Thread B revives a BT_CLOSED + SOCK_ZAPPED socket back to

BT_CONNECT. Subsequent cleanup triggers double sock_put() and

use-after-free. Meanwhile conn1 is leaked as it was orphaned

when sco_conn_del() cleared the association.

Fix this by:

- Moving lock_sock() before the sk_state/sk_type checks in

sco_sock_connect() to serialize concurrent connect attempts

- Fixing the sk_type != SOCK_SEQPACKET check to actually

return the error instead of just assigning it

- Adding a state re-check in sco_connect() after lock_sock()

to catch state changes during the window between the locks

- Adding sco_pi(sk)->conn check in sco_chan_add() to prevent

double-attach of a socket to multiple connections

- Adding hci_conn_drop() on sco_chan_add failure to prevent

HCI connection leaks