CVE-2021-3640Public exploit

Privilege escalation via Bluetooth SCO use-after-free

Published Mar 3, 2022 · Updated Aug 3, 2024

Use-after-free in the Linux Kernel through 5.15.3 allows privileged local users to escalate privileges or crash the system. During an SCO send, userfaultfd can suspend memcpy_from_msg while sco_conn_del frees the shared sco_conn object, after which hci_send_sco dereferences it. Exploitation requires CAP_NET_ADMIN, a fabricated SCO connection, a controlled faulting page, and controller detachment; the demonstrated outcome is a kernel crash.

CVSS severity7.0
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux Kernel through 5.15.3 allows privileged local users to escalate privileges or crash the system. During an SCO send, userfaultfd can suspend memcpy_from_msg while sco_conn_del frees the shared sco_conn object, after which hci_send_sco dereferences it. Exploitation requires CAP_NET_ADMIN, a fabricated SCO connection, a controlled faulting page, and controller detachment; the demonstrated outcome is a kernel crash.

The record

CVE
CVE-2021-3640
Published
Mar 3, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362, CWE-416, T1068, T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 3, 2022CVE 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=Affects kernel v5.15.3 and prior, Fixed in v5.16-rc1 and above.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=Affects kernel v5.15.3 and prior, Fixed in v5.16-rc1 and above.

Published CVSS scores

7.0NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0OracleCVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
6.9NIST NVDAV:L/AC:M/Au:N/C:C/I:C/A:C

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-416Use After Free
T1068Exploitation for Privilege Escalation
T1499.004Application or System Exploitation

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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