CVE-2023-53673: Bluetooth: hci_event: call disconnect callback before deleting conn

Vulnerability summary

CVE-2023-53673 is a high (CVSS 8.8) Use After Free vulnerability in linux. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 16.3% of scored vulnerabilities.

Timeline

1. 07-10-2025
   PublishedVulnerability first disclosed.
2. 05-08-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_event: call disconnect callback before deleting conn In hci_cs_disconnect, we do hci_conn_del even if disconnection failed. ISO, L2CAP and SCO connections refer to the hci_conn without hci_conn_get, so disconn_cfm must be called so they can clean up their conn, otherwise use-after-free occurs. ISO: ========================================================== iso_sock_connect:880: sk 00000000eabd6557 iso_connect_cis:356: 70:1a:b8:98:ff:a2 -> 28:3d:c2:4a:7e:da ... iso_conn_add:140: hcon 000000001696f1fd conn 00000000b6251073 hci_dev_put:1487: hci0 orig refcnt 17 __iso_chan_add:214: conn 00000000b6251073 iso_sock_clear_timer:117: sock 00000000eabd6557 state 3 ... hci_rx_work:4085: hci0 Event packet hci_event_packet:7601: hci0: event 0x0f hci_cmd_status_evt:4346: hci0: opcode 0x0406 hci_cs_disconnect:2760: hci0: status 0x0c hci_sent_cmd_data:3107: hci0 opcode 0x0406 hci_conn_del:1151: hci0 hcon 000000001696f1fd handle 2560 hci_conn_unlink:1102: hci0: hcon 000000001696f1fd hci_conn_drop:1451: hcon 00000000d8521aaf orig refcnt 2 hci_chan_list_flush:2780: hcon 000000001696f1fd hci_dev_put:1487: hci0 orig refcnt 21 hci_dev_put:1487: hci0 orig refcnt 20 hci_req_cmd_complete:3978: opcode 0x0406 status 0x0c ... <no iso_* activity on sk/conn> ... iso_sock_sendmsg:1098: sock 00000000dea5e2e0, sk 00000000eabd6557 BUG: kernel NULL pointer dereference, address: 0000000000000668 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014 RIP: 0010:iso_sock_sendmsg (net/bluetooth/iso.c:1112) bluetooth ========================================================== L2CAP: ================================================================== hci_cmd_status_evt:4359: hci0: opcode 0x0406 hci_cs_disconnect:2760: hci0: status 0x0c hci_sent_cmd_data:3085: hci0 opcode 0x0406 hci_conn_del:1151: hci0 hcon ffff88800c999000 handle 3585 hci_conn_unlink:1102: hci0: hcon ffff88800c999000 hci_chan_list_flush:2780: hcon ffff88800c999000 hci_chan_del:2761: hci0 hcon ffff88800c999000 chan ffff888018ddd280 ... BUG: KASAN: slab-use-after-free in hci_send_acl+0x2d/0x540 [bluetooth] Read of size 8 at addr ffff888018ddd298 by task bluetoothd/1175 CPU: 0 PID: 1175 Comm: bluetoothd Tainted: G E 6.4.0-rc4+ #2 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x5b/0x90 print_report+0xcf/0x670 ? __virt_addr_valid+0xf8/0x180 ? hci_send_acl+0x2d/0x540 [bluetooth] kasan_report+0xa8/0xe0 ? hci_send_acl+0x2d/0x540 [bluetooth] hci_send_acl+0x2d/0x540 [bluetooth] ? __pfx___lock_acquire+0x10/0x10 l2cap_chan_send+0x1fd/0x1300 [bluetooth] ? l2cap_sock_sendmsg+0xf2/0x170 [bluetooth] ? __pfx_l2cap_chan_send+0x10/0x10 [bluetooth] ? lock_release+0x1d5/0x3c0 ? mark_held_locks+0x1a/0x90 l2cap_sock_sendmsg+0x100/0x170 [bluetooth] sock_write_iter+0x275/0x280 ? __pfx_sock_write_iter+0x10/0x10 ? __pfx___lock_acquire+0x10/0x10 do_iter_readv_writev+0x176/0x220 ? __pfx_do_iter_readv_writev+0x10/0x10 ? find_held_lock+0x83/0xa0 ? selinux_file_permission+0x13e/0x210 do_iter_write+0xda/0x340 vfs_writev+0x1b4/0x400 ? __pfx_vfs_writev+0x10/0x10 ? __seccomp_filter+0x112/0x750 ? populate_seccomp_data+0x182/0x220 ? __fget_light+0xdf/0x100 ? do_writev+0x19d/0x210 do_writev+0x19d/0x210 ? __pfx_do_writev+0x10/0x10 ? mark_held_locks+0x1a/0x90 do_syscall_64+0x60/0x90 ? lockdep_hardirqs_on_prepare+0x149/0x210 ? do_syscall_64+0x6c/0x90 ? lockdep_hardirqs_on_prepare+0x149/0x210 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7ff45cb23e64 Code: 15 d1 1f 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 80 3d 9d a7 0d 00 00 74 13 b8 14 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89 RSP: 002b:00007fff21ae09b8 EFLAGS: 00000202 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: ---truncated---

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.