In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: SCO: give the socket its own sco_conn reference
sco_conn_del() drops a reference it does not own. It takes one transient
reference via sco_conn_hold_unless_zero() and releases it with the
sco_conn_put() that follows sco_sock_hold(); the additional put in the
!sk branch releases a second one:
conn = sco_conn_hold_unless_zero(conn);
...
sk = sco_sock_hold(conn);
sco_conn_unlock(conn);
sco_conn_put(conn);
if (!sk) {
sco_conn_put(conn);
return;
}
When close() races the controller's Disconnection Complete, sco_chan_del()
clears conn->sk and drops the socket's reference while sco_conn_del() is
running. sco_conn_del() then sees sk == NULL, its own put drops the count
to zero and frees the conn, and the second put writes to the freed kref:
BUG: KASAN: slab-use-after-free in sco_conn_put.part.0+0x1a/0x190
Write of size 4 at addr ffff8881099dec74 by task kworker/u17:3/413
Workqueue: hci1 hci_rx_work
Call Trace:
sco_conn_put.part.0+0x1a/0x190
hci_disconn_complete_evt+0x1ee/0x3e0
hci_event_packet+0x54a/0x650
hci_rx_work+0x321/0x3d0
Allocated by task 413:
sco_conn_add+0x72/0x1a0
sco_connect_cfm+0x88/0x670
Freed by task 413:
sco_conn_del.isra.0+0x3f/0xf0
hci_disconn_complete_evt+0x1ee/0x3e0
refcount_t: underflow; use-after-free.
The root cause is that the socket stores the connection without holding a
reference of its own. __sco_chan_add() does:
sco_pi(sk)->conn = conn;
so the socket borrows whatever reference its caller happened to hold, and
the callers paper over that with ad-hoc holds and puts. Give the socket a
counted reference instead: __sco_chan_add() takes one and it is released
together with the channel (sco_chan_del()) and in sco_sock_destruct().
With the socket holding its own reference, sco_conn_del() no longer needs
the extra put and the redundant hold in sco_conn_ready() goes away.
Making the socket own its reference means the connection is now actually
freed on the error paths of sco_connect() where it used to leak, which in
turn runs sco_conn_free() and its hci_conn_drop(conn->hcon). To keep the
hci_conn accounting balanced, make that ownership explicit as well:
sco_conn_add() consumes one hci_conn reference and the sco_conn owns it for
its lifetime. sco_connect() hands over the reference returned by
hci_connect_sco() and no longer drops it on the error paths;
sco_connect_cfm(), which is not given a reference, takes one with
hci_conn_hold() before handing it to sco_conn_add() (and drops it again if
the allocation fails); and the explicit hci_conn_hold() in sco_conn_ready()
is removed. Every reference then has a single, clear owner.
Bluetooth: SCO: give the socket its own sco_conn reference
sco_conn_del() drops a reference it does not own. It takes one transient
reference via sco_conn_hold_unless_zero() and releases it with the
sco_conn_put() that follows sco_sock_hold(); the additional put in the
!sk branch releases a second one:
conn = sco_conn_hold_unless_zero(conn);
...
sk = sco_sock_hold(conn);
sco_conn_unlock(conn);
sco_conn_put(conn);
if (!sk) {
sco_conn_put(conn);
return;
}
When close() races the controller's Disconnection Complete, sco_chan_del()
clears conn->sk and drops the socket's reference while sco_conn_del() is
running. sco_conn_del() then sees sk == NULL, its own put drops the count
to zero and frees the conn, and the second put writes to the freed kref:
BUG: KASAN: slab-use-after-free in sco_conn_put.part.0+0x1a/0x190
Write of size 4 at addr ffff8881099dec74 by task kworker/u17:3/413
Workqueue: hci1 hci_rx_work
Call Trace:
sco_conn_put.part.0+0x1a/0x190
hci_disconn_complete_evt+0x1ee/0x3e0
hci_event_packet+0x54a/0x650
hci_rx_work+0x321/0x3d0
Allocated by task 413:
sco_conn_add+0x72/0x1a0
sco_connect_cfm+0x88/0x670
Freed by task 413:
sco_conn_del.isra.0+0x3f/0xf0
hci_disconn_complete_evt+0x1ee/0x3e0
refcount_t: underflow; use-after-free.
The root cause is that the socket stores the connection without holding a
reference of its own. __sco_chan_add() does:
sco_pi(sk)->conn = conn;
so the socket borrows whatever reference its caller happened to hold, and
the callers paper over that with ad-hoc holds and puts. Give the socket a
counted reference instead: __sco_chan_add() takes one and it is released
together with the channel (sco_chan_del()) and in sco_sock_destruct().
With the socket holding its own reference, sco_conn_del() no longer needs
the extra put and the redundant hold in sco_conn_ready() goes away.
Making the socket own its reference means the connection is now actually
freed on the error paths of sco_connect() where it used to leak, which in
turn runs sco_conn_free() and its hci_conn_drop(conn->hcon). To keep the
hci_conn accounting balanced, make that ownership explicit as well:
sco_conn_add() consumes one hci_conn reference and the sco_conn owns it for
its lifetime. sco_connect() hands over the reference returned by
hci_connect_sco() and no longer drops it on the error paths;
sco_connect_cfm(), which is not given a reference, takes one with
hci_conn_hold() before handing it to sco_conn_add() (and drops it again if
the allocation fails); and the explicit hci_conn_hold() in sco_conn_ready()
is removed. Every reference then has a single, clear owner.
Metrics
Affected Vendors & Products
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Advisories
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 28 Aug 2026 11:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-762 |
Fri, 28 Aug 2026 07:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: Bluetooth: SCO: give the socket its own sco_conn reference sco_conn_del() drops a reference it does not own. It takes one transient reference via sco_conn_hold_unless_zero() and releases it with the sco_conn_put() that follows sco_sock_hold(); the additional put in the !sk branch releases a second one: conn = sco_conn_hold_unless_zero(conn); ... sk = sco_sock_hold(conn); sco_conn_unlock(conn); sco_conn_put(conn); if (!sk) { sco_conn_put(conn); return; } When close() races the controller's Disconnection Complete, sco_chan_del() clears conn->sk and drops the socket's reference while sco_conn_del() is running. sco_conn_del() then sees sk == NULL, its own put drops the count to zero and frees the conn, and the second put writes to the freed kref: BUG: KASAN: slab-use-after-free in sco_conn_put.part.0+0x1a/0x190 Write of size 4 at addr ffff8881099dec74 by task kworker/u17:3/413 Workqueue: hci1 hci_rx_work Call Trace: sco_conn_put.part.0+0x1a/0x190 hci_disconn_complete_evt+0x1ee/0x3e0 hci_event_packet+0x54a/0x650 hci_rx_work+0x321/0x3d0 Allocated by task 413: sco_conn_add+0x72/0x1a0 sco_connect_cfm+0x88/0x670 Freed by task 413: sco_conn_del.isra.0+0x3f/0xf0 hci_disconn_complete_evt+0x1ee/0x3e0 refcount_t: underflow; use-after-free. The root cause is that the socket stores the connection without holding a reference of its own. __sco_chan_add() does: sco_pi(sk)->conn = conn; so the socket borrows whatever reference its caller happened to hold, and the callers paper over that with ad-hoc holds and puts. Give the socket a counted reference instead: __sco_chan_add() takes one and it is released together with the channel (sco_chan_del()) and in sco_sock_destruct(). With the socket holding its own reference, sco_conn_del() no longer needs the extra put and the redundant hold in sco_conn_ready() goes away. Making the socket own its reference means the connection is now actually freed on the error paths of sco_connect() where it used to leak, which in turn runs sco_conn_free() and its hci_conn_drop(conn->hcon). To keep the hci_conn accounting balanced, make that ownership explicit as well: sco_conn_add() consumes one hci_conn reference and the sco_conn owns it for its lifetime. sco_connect() hands over the reference returned by hci_connect_sco() and no longer drops it on the error paths; sco_connect_cfm(), which is not given a reference, takes one with hci_conn_hold() before handing it to sco_conn_add() (and drops it again if the allocation fails); and the explicit hci_conn_hold() in sco_conn_ready() is removed. Every reference then has a single, clear owner. | |
| Title | Bluetooth: SCO: give the socket its own sco_conn reference | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-28T06:52:50.099Z
Reserved: 2026-08-26T14:34:25.784Z
Link: CVE-2026-80683
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-28T08:16:53.737
Modified: 2026-08-28T08:16:53.737
Link: CVE-2026-80683
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-28T13:45:17Z
Weaknesses