Linux Kernel 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_stateBT_OPEN sk_stateBT_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