CVE-2021-3564Public exploit

System crash via HCI command cleanup race

Published Jun 8, 2021 · Updated Aug 3, 2024

Double-free memory corruption in Linux Kernel 3.13 and later allows local users to crash the system through a malicious HCI TTY device. In hci_dev_do_open, hci_rx_work can requeue hci_cmd_work after it was flushed, racing cleanup so hdev->sent_cmd is freed twice. Attaching a crafted HCI TTY device needs no extra privileges; demonstrated impact is kernel memory corruption and a system crash.

CVSS severity5.5
Medium
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free memory corruption in Linux Kernel 3.13 and later allows local users to crash the system through a malicious HCI TTY device. In hci_dev_do_open, hci_rx_work can requeue hci_cmd_work after it was flushed, racing cleanup so hdev->sent_cmd is freed twice. Attaching a crafted HCI TTY device needs no extra privileges; demonstrated impact is kernel memory corruption and a system crash.

The record

CVE
CVE-2021-3564
Published
Jun 8, 2021
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-415, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=All Linux kernel versions starting from 3.13

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=All Linux kernel versions starting from 3.13

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitPublished

Weakness, pattern, technique

CWE-415Double Free
T1499Endpoint Denial of Service

Public exploit references

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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