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

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/7e296ffdab5bdab718dff7c14288fdcb9154fa27
• https://git.kernel.org/stable/c/8a5b0135d4a5d9683203a3d9a12a711ccec5936b
• https://git.kernel.org/stable/c/98c8d3bfdaa657d8f472dbbebd7ea8cd816d8a8d
• https://git.kernel.org/stable/c/adb90cd0f9f7a8d438fcb93354040fbafc5ae2a0
• https://git.kernel.org/stable/c/d002bd11024bd231bcb606877e33951ffb7bed14
• https://git.kernel.org/stable/c/dabf22269242e2f2bf44c43fcdc2fa763df7f9cc