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Response snapshot Oct 30, 2026, 19:11 UTC

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VulnerabilityCVE-2026-31771

Linux kernel: Bluetooth: hci_event: move wake reason storage into validated event handlers

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.

At a glance

Exploited
Not known
Severity
8.1 High (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-31771 (opens a new tab)

What happened

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().

Continue reading

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().

Scores and how they were measured

CVSS base severity

8.1

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 24.6%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-31771 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-31771, scored 2026-10-30. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Linux kernel: Bluetooth: hci_event: move wake reason storage into validated event handlers (CVE-2026-31771). https://kevwire.com/record/CVE-2026-31771

MLA

"Linux kernel: Bluetooth: hci_event: move wake reason storage into validated event handlers (CVE-2026-31771)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-31771.

Chicago

KEVWire. "Linux kernel: Bluetooth: hci_event: move wake reason storage into validated event handlers (CVE-2026-31771)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-31771.

Evidence summary (plain text)

Linux kernel: Bluetooth: hci_event: move wake reason storage into validated event handlers (May 1, 2026).
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.
CVSS 8.1 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-31771).
EPSS 0.3% for the following 30 days, scored Oct 30, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-31771&date=2026-10-30).
Sources:
NVD CVE-2026-31771: https://nvd.nist.gov/vuln/detail/CVE-2026-31771
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T13:06:45.042Z&lastModEndDate=2026-10-30T14:50:57.069Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T12:22:16.957Z&lastModEndDate=2026-10-30T14:05:57.373Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T11:45:59.009Z&lastModEndDate=2026-10-30T13:20:57.281Z&resultsPerPage=500&startIndex=0
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-31771&date=2026-10-30
Record ID: CVE-2026-31771.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 14:52 UTC. Ingestion is not an independent editorial investigation.

NVD status: Modified. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

Record JSON

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Record details

Record detail