CVE-2026-98455 Bluetooth: RFCOMM: fix NULL dereference of dlc->session in RFCOMM_CONNINFO
A local attacker with Bluetooth access can cause a kernel crash via a NULL pointer dereference in the RFCOMM module when deferred setup is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98455?
CVE-2026-98455 is a vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-98455?
How do I fix CVE-2026-98455?
Apply the vendor's patch.
Is CVE-2026-98455 being exploited?
There is no known exploitation of CVE-2026-98455 in the wild and no public exploit code.
Sources
Also known as AZL-109059, BELL-CVE-2026-98455, DEBIAN-CVE-2026-98455, GHSA-5qmc-rg3w-hx9m, UBUNTU-CVE-2026-98455.