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Linux KernelOperating system · Linux

CVE-2023-53252

HIGH · 7.8 CVSS v3.1 Published 2025-09-15
Fix available
A fix is available. Upgrade to 6.1.42 / 6.4.7 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: use RCU for hci_conn_params and iterate safely in hci_sync hci_update_accept_list_sync iterates over hdev->pend_le_conns and hdev->pend_le_reports, and waits for controller events in the loop body, without holding hdev lock. Meanwhile, these lists and the items may be modified e.g. by le_scan_cleanup. This can invalidate the list cursor or any other item in the list, resulting to invalid behavior (eg use-after-free). Use RCU for the hci_conn_params action lists. Since the loop bodies in hci_sync block and we cannot use RCU or hdev->lock for the whole loop, copy list items first and then iterate on the copy. Only the flags field is written from elsewhere, so READ_ONCE/WRITE_ONCE should guarantee we read valid values. Free params everywhere with hci_conn_params_free so the cleanup is guaranteed to be done properly. This fixes the following, which can be triggered e.g. by BlueZ new mgmt-tester case "Add + Remove Device Nowait - Success", or by changing hci_le_set_cig_params to always return false, and running iso-tester: ================================================================== BUG: KASAN: slab-use-after-free in hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841) Read of size 8 at addr ffff888001265018 by task kworker/u3:0/32 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014 Workqueue: hci0 hci_cmd_sync_work Call Trace: <TASK> dump_stack_lvl (./arch/x86/include/asm/irqflags.h:134 lib/dump_stack.c:107) print_report (mm/kasan/report.c:320 mm/kasan/report.c:430) ? __virt_addr_valid (./include/linux/mmzone.h:1915 ./include/linux/mmzone.h:2011 arch/x86/mm/physaddr.c:65) ? hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841) kasan_report (mm/kasan/report.c:538) ? hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841) hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841) ? __pfx_hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2780) ? mutex_lock (kernel/locking/mutex.c:282) ? __pfx_mutex_lock (kernel/locking/mutex.c:282) ? __pfx_mutex_unlock (kernel/locking/mutex.c:538) ? __pfx_update_passive_scan_sync (net/bluetooth/hci_sync.c:2861) hci_cmd_sync_work (net/bluetooth/hci_sync.c:306) process_one_work (./arch/x86/include/asm/preempt.h:27 kernel/workqueue.c:2399) worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2538) ? __pfx_worker_thread (kernel/workqueue.c:2480) kthread (kernel/kthread.c:376) ? __pfx_kthread (kernel/kthread.c:331) ret_from_fork (arch/x86/entry/entry_64.S:314) </TASK> Allocated by task 31: kasan_save_stack (mm/kasan/common.c:46) kasan_set_track (mm/kasan/common.c:52) __kasan_kmalloc (mm/kasan/common.c:374 mm/kasan/common.c:383) hci_conn_params_add (./include/linux/slab.h:580 ./include/linux/slab.h:720 net/bluetooth/hci_core.c:2277) hci_connect_le_scan (net/bluetooth/hci_conn.c:1419 net/bluetooth/hci_conn.c:1589) hci_connect_cis (net/bluetooth/hci_conn.c:2266) iso_connect_cis (net/bluetooth/iso.c:390) iso_sock_connect (net/bluetooth/iso.c:899) __sys_connect (net/socket.c:2003 net/socket.c:2020) __x64_sys_connect (net/socket.c:2027) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) Freed by task 15: kasan_save_stack (mm/kasan/common.c:46) kasan_set_track (mm/kasan/common.c:52) kasan_save_free_info (mm/kasan/generic.c:523) __kasan_slab_free (mm/kasan/common.c:238 mm/kasan/common.c:200 mm/kasan/common.c:244) __kmem_cache_free (mm/slub.c:1807 mm/slub.c:3787 mm/slub.c:3800) hci_conn_params_del (net/bluetooth/hci_core.c:2323) le_scan_cleanup (net/bluetooth/hci_conn.c:202) process_one_work (./arch/x86/include/asm/preempt. ---truncated---

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.17, < 6.1.42>= 6.2, < 6.4.7= 6.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.1.42 / 6.4.7 or later
Fixed in 6.1.426.4.7
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to Linux kernel 6.1.42, 6.4.7, or 6.5.1 (or later) depending on your current branch

  1. Identify the current running kernel version using `uname -r`
  2. Determine which major kernel branch you are on (e.g., 5.17+, 6.1.x, 6.2.x, 6.3.x, or 6.5.x)
  3. For kernels >= 5.17 and < 6.1.42: upgrade to kernel version 6.1.42 or later
  4. For kernels >= 6.2 and < 6.4.7: upgrade to kernel version 6.4.7 or later
  5. For kernel = 6.5: upgrade to kernel version 6.5.1 or later
  6. Reboot the system to load the fixed kernel
  7. Verify the fix is applied by checking the kernel version matches or exceeds the fixed versions listed above
Caveat Kernel upgrades may require system reboots and could have compatibility implications with custom modules or specific hardware drivers; ensure backup and test in non-production environments first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-53252 in production — separate from our analysis above.

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