In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO
The RFCOMM_CONNINFO getsockopt handler accepts a socket that is not
connected as long as deferred setup is enabled:
if (sk->sk_state != BT_CONNECTED &&
!rfcomm_pi(sk)->dlc->defer_setup) {
err = -ENOTCONN;
break;
}
l2cap_sk = rfcomm_pi(sk)->dlc->session->sock->sk;
dlc->defer_setup is set in rfcomm_sock_init() when rfcomm_connect_ind()
creates a child socket for an incoming connection on a listening socket
that has BT_DEFER_SETUP enabled. It is never cleared afterwards. The
session, however, can go away underneath it.
rfcomm_recv_disc() forces the dlc state before tearing it down:
d->state = BT_CLOSED;
__rfcomm_dlc_close(d, err);
The RFCOMM_DEFER_SETUP early return in __rfcomm_dlc_close() only covers
BT_CONNECT, BT_CONFIG, BT_OPEN and BT_CONNECT2, so with the state
already BT_CLOSED that switch does not match and the function falls
through to rfcomm_dlc_unlink(), which sets d->session = NULL, while
d->defer_setup stays 1.
A getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted socket after
that point therefore skips the -ENOTCONN path -- sk->sk_state is
BT_CLOSED, but dlc->defer_setup is still set -- and dereferences the
NULL session. No race is needed: once the DISC has been processed, the
dereference is unconditional.
Reproduced on a KASAN kernel under QEMU with a BR/EDR peer emulated over
/dev/vhci: the peer brings up an ACL link, opens L2CAP on the RFCOMM
PSM, starts a session and sends SABM for a channel bound with
BT_DEFER_SETUP, and sends DISC for that dlci after the socket has been
accepted. getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted
socket then hits:
Oops: general protection fault, probably for non-canonical address
0xdffffc0000000002: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 UID: 0 PID: 150 Comm: init Tainted: G B 7.3.0-rc3-g5dd1818b15d9
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:rfcomm_sock_getsockopt+0x529/0x780
Call Trace:
<TASK>
do_sock_getsockopt+0x3ad/0x7d0
__sys_getsockopt+0x10e/0x1b0
__x64_sys_getsockopt+0xc2/0x160
do_syscall_64+0xda/0x4b0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
0x10 is the offset of sock in struct rfcomm_session;
rfcomm_sock_getsockopt_old() is inlined into rfcomm_sock_getsockopt().
Commit 43a556b2fd43 ("Bluetooth: RFCOMM: take rfcomm_mutex for the
deferred setup accept") fixed the same "a remote DISC clears the session
while deferred setup is still flagged" problem in rfcomm_dlc_accept();
this is the remaining instance of it, in the getsockopt path.
Deferred setup only leaves a socket usable here once it has reached
BT_CONNECT2, so restrict the exception to that state and check that a
session is actually present before following it.
Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO
The RFCOMM_CONNINFO getsockopt handler accepts a socket that is not
connected as long as deferred setup is enabled:
if (sk->sk_state != BT_CONNECTED &&
!rfcomm_pi(sk)->dlc->defer_setup) {
err = -ENOTCONN;
break;
}
l2cap_sk = rfcomm_pi(sk)->dlc->session->sock->sk;
dlc->defer_setup is set in rfcomm_sock_init() when rfcomm_connect_ind()
creates a child socket for an incoming connection on a listening socket
that has BT_DEFER_SETUP enabled. It is never cleared afterwards. The
session, however, can go away underneath it.
rfcomm_recv_disc() forces the dlc state before tearing it down:
d->state = BT_CLOSED;
__rfcomm_dlc_close(d, err);
The RFCOMM_DEFER_SETUP early return in __rfcomm_dlc_close() only covers
BT_CONNECT, BT_CONFIG, BT_OPEN and BT_CONNECT2, so with the state
already BT_CLOSED that switch does not match and the function falls
through to rfcomm_dlc_unlink(), which sets d->session = NULL, while
d->defer_setup stays 1.
A getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted socket after
that point therefore skips the -ENOTCONN path -- sk->sk_state is
BT_CLOSED, but dlc->defer_setup is still set -- and dereferences the
NULL session. No race is needed: once the DISC has been processed, the
dereference is unconditional.
Reproduced on a KASAN kernel under QEMU with a BR/EDR peer emulated over
/dev/vhci: the peer brings up an ACL link, opens L2CAP on the RFCOMM
PSM, starts a session and sends SABM for a channel bound with
BT_DEFER_SETUP, and sends DISC for that dlci after the socket has been
accepted. getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted
socket then hits:
Oops: general protection fault, probably for non-canonical address
0xdffffc0000000002: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 UID: 0 PID: 150 Comm: init Tainted: G B 7.3.0-rc3-g5dd1818b15d9
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:rfcomm_sock_getsockopt+0x529/0x780
Call Trace:
<TASK>
do_sock_getsockopt+0x3ad/0x7d0
__sys_getsockopt+0x10e/0x1b0
__x64_sys_getsockopt+0xc2/0x160
do_syscall_64+0xda/0x4b0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
0x10 is the offset of sock in struct rfcomm_session;
rfcomm_sock_getsockopt_old() is inlined into rfcomm_sock_getsockopt().
Commit 43a556b2fd43 ("Bluetooth: RFCOMM: take rfcomm_mutex for the
deferred setup accept") fixed the same "a remote DISC clears the session
while deferred setup is still flagged" problem in rfcomm_dlc_accept();
this is the remaining instance of it, in the getsockopt path.
Deferred setup only leaves a socket usable here once it has reached
BT_CONNECT2, so restrict the exception to that state and check that a
session is actually present before following it.
Metrics
Affected Vendors & Products
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Fixes
Solution
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Workaround
No workaround given by the vendor.
References
History
Sun, 18 Oct 2026 17:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-476 |
Sun, 18 Oct 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO The RFCOMM_CONNINFO getsockopt handler accepts a socket that is not connected as long as deferred setup is enabled: if (sk->sk_state != BT_CONNECTED && !rfcomm_pi(sk)->dlc->defer_setup) { err = -ENOTCONN; break; } l2cap_sk = rfcomm_pi(sk)->dlc->session->sock->sk; dlc->defer_setup is set in rfcomm_sock_init() when rfcomm_connect_ind() creates a child socket for an incoming connection on a listening socket that has BT_DEFER_SETUP enabled. It is never cleared afterwards. The session, however, can go away underneath it. rfcomm_recv_disc() forces the dlc state before tearing it down: d->state = BT_CLOSED; __rfcomm_dlc_close(d, err); The RFCOMM_DEFER_SETUP early return in __rfcomm_dlc_close() only covers BT_CONNECT, BT_CONFIG, BT_OPEN and BT_CONNECT2, so with the state already BT_CLOSED that switch does not match and the function falls through to rfcomm_dlc_unlink(), which sets d->session = NULL, while d->defer_setup stays 1. A getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted socket after that point therefore skips the -ENOTCONN path -- sk->sk_state is BT_CLOSED, but dlc->defer_setup is still set -- and dereferences the NULL session. No race is needed: once the DISC has been processed, the dereference is unconditional. Reproduced on a KASAN kernel under QEMU with a BR/EDR peer emulated over /dev/vhci: the peer brings up an ACL link, opens L2CAP on the RFCOMM PSM, starts a session and sends SABM for a channel bound with BT_DEFER_SETUP, and sends DISC for that dlci after the socket has been accepted. getsockopt(SOL_RFCOMM, RFCOMM_CONNINFO) on the accepted socket then hits: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 UID: 0 PID: 150 Comm: init Tainted: G B 7.3.0-rc3-g5dd1818b15d9 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:rfcomm_sock_getsockopt+0x529/0x780 Call Trace: <TASK> do_sock_getsockopt+0x3ad/0x7d0 __sys_getsockopt+0x10e/0x1b0 __x64_sys_getsockopt+0xc2/0x160 do_syscall_64+0xda/0x4b0 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> 0x10 is the offset of sock in struct rfcomm_session; rfcomm_sock_getsockopt_old() is inlined into rfcomm_sock_getsockopt(). Commit 43a556b2fd43 ("Bluetooth: RFCOMM: take rfcomm_mutex for the deferred setup accept") fixed the same "a remote DISC clears the session while deferred setup is still flagged" problem in rfcomm_dlc_accept(); this is the remaining instance of it, in the getsockopt path. Deferred setup only leaves a socket usable here once it has reached BT_CONNECT2, so restrict the exception to that state and check that a session is actually present before following it. | |
| Title | Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO | |
| 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: 2026-10-18T15:15:04.988Z
Reserved: 2026-09-25T10:25:14.350Z
Link: CVE-2026-98455
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:16:55.863
Modified: 2026-10-18T16:16:55.863
Link: CVE-2026-98455
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-10-18T17:00:09Z
Weaknesses