CVE-2026-99012

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

Bluetooth: ISO: Serialize concurrent connect calls

iso sock connect() checks the socket state before taking the socket lock and drops the lock again before setting up a connection. Two callers can both pass the admission check while the socket is open or bound.

Caller A can copy its destination for route selection, then caller B can replace the socket destination before A binds or connects the CIS. A then uses B's destination with the route selected for its own request. B can also proceed after A attaches a connection and sets BT CONNECT. For deferred BIS setup, B can bind a second BIS and overwrite iso pi(sk)->conn, leaving the first connection's reference and conn->sk back-pointer stranded. Concurrent CIS connects can likewise replace the socket's connection. Later teardown only detaches the current connection, so a callback on the old connection can race with socket release and access a freed socket.

KASAN reported:

BUG: KASAN: slab-use-after-free in iso sock hold+0xf7/0x1b0 Call Trace: iso sock hold+0xf7/0x1b0 iso conn del+0x7b/0x1d0 iso connect cfm+0x186/0x16a0 hci conn failed+0x154/0x280 hci abort conn sync+0x3dc/0x7d0 hci cmd sync work+0x173/0x300

Allocated by task 121: sk alloc+0x2b/0x6d0 bt sock alloc+0x29/0x370 iso sock alloc.constprop.0+0x19/0x300 iso sock create+0x94/0x100

Freed by task 121: kfree+0x121/0x3c0 sk destruct+0x42b/0x540 iso sock release+0x29d/0x340 sock release+0xa1/0x260

Check admission under the socket lock and mark the connect operation in progress before publishing its destination. Keep that flag set across route lookup and connection setup, rejecting another connect with -EBADFD before it can change the destination or attach a connection. Clear the flag after either helper returns, including on failure, so a failed setup can be retried.

A separate flag is needed because the socket lock must be released before acquiring the HCI device lock, while BT CONNECT requires an attached connection. Keep the existing state transitions and the deferred CIS completion through iso sock recvmsg().

Reject an existing socket attachment in iso chan add() before taking a new reference or publishing either pointer, so every caller preserves the connection association. Keep the same-socket, same-connection success case for deferred CIS setup. Reject an attached socket before BIS setup so a reusable BIS is not claimed before the attachment is rejected.

In CIS setup, reject a different HCI connection before iso conn add() and drop the per-attempt HCI hold directly. An unowned iso conn may still carry another reference after detachment, so its destruction cannot be relied on to release that hold.

iso listen bis() creates a fresh PA HCI/ISO pair under the device lock, so the temporary iso conn put() frees the ISO candidate and drops its HCI hold on rejection. iso conn ready() uses a freshly allocated, unpublished child with no connection, making the socket-side rejection unreachable.