CVE-2026-31771

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().

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://git.kernel.org/stable/c/2b2bf47cd75518c36fa2d41380e4a40641cc89cd
• https://git.kernel.org/stable/c/86c8d07a64d553c41e213b52650020010f9ef23e
• https://www.suse.com/security/cve/CVE-2026-31771.html
• https://security-tracker.debian.org/tracker/CVE-2026-31771
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31771