---
id: "CVE-2026-98455"
kind: "vulnerability"
aliases: ["CVE-2026-98455"]
title: "Linux kernel: RFCOMM getsockopt crashes on a socket after remote disconnect"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["bluetooth", "kernel", "linux", "other", "rfcomm"]
not_affected_if: ["no-bluetooth", "rfcomm-unused"]
published_at: "2026-10-18T16:16:55+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:27:20+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98455", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel: RFCOMM getsockopt crashes on a socket after remote disconnect

After a remote DISC on an RFCOMM Bluetooth socket that was accepted with deferred setup, a getsockopt call on RFCOMM_CONNINFO dereferences a NULL session pointer, which crashes the kernel. The sources describe a kernel NULL pointer dereference; the impact beyond denial of service is not stated.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the upstream fix from commit `43a556b2fd43` or the mainline change that restricts the RFCOMM_CONNINFO deferred-setup exception to BT_CONNECT2 and checks for a session.
- Check your distribution's kernel advisory for the fixed package version: unknown

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98455

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_