CVE-2021-47038

Local Bluetooth hang via circular lock dependency

Published Feb 28, 2024 · Updated May 11, 2026

Improper locking in Linux kernel Bluetooth allows local users to hang Bluetooth processing via an L2CAP BT_PHY socket-option query. hci_conn_get_phy acquires hdev->lock while the calling getsockopt path holds the Bluetooth socket lock, completing a circular dependency through channel locks. Local low-privileged access is required, and the bounded consequence is an availability-only deadlock in Bluetooth operations.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in Linux kernel Bluetooth allows local users to hang Bluetooth processing via an L2CAP BT_PHY socket-option query. hci_conn_get_phy acquires hdev->lock while the calling getsockopt path holds the Bluetooth socket lock, completing a circular dependency through channel locks. Local low-privileged access is required, and the bounded consequence is an availability-only deadlock in Bluetooth operations.

The record

CVE
CVE-2021-47038
Published
Feb 28, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.7
  2. Affected versionversion=eab2404ba798a8efda2a970f44071c3406d94e57 <17486960d79b900c45e0bb8fbcac0262848582ba
  3. Affected versionversion=eab2404ba798a8efda2a970f44071c3406d94e57 <332e69eb3bd90370f2d9f2c2ca7974ff523dea17
  4. Affected versionversion=eab2404ba798a8efda2a970f44071c3406d94e57 <7cc0ba67883c6c8d3bddb283f56c167fc837a555
  5. Affected versionversion=eab2404ba798a8efda2a970f44071c3406d94e57 <fee71f480bc1dec5f6ae3b0b185ff12a62bceabc

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.7; version=eab2404ba798a8efda2a970f44071c3406d94e57 <17486960d79b900c45e0bb8fbcac0262848582ba; version=eab2404ba798a8efda2a970f44071c3406d94e57 <332e69eb3bd90370f2d9f2c2ca7974ff523dea17; version=eab2404ba798a8efda2a970f44071c3406d94e57 <7cc0ba67883c6c8d3bddb283f56c167fc837a555; version=eab2404ba798a8efda2a970f44071c3406d94e57 <fee71f480bc1dec5f6ae3b0b185ff12a62bceabc

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-667Improper Locking
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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