CVE-2021-39640

Local privilege escalation via USB queue locking

Published Dec 15, 2021 · Updated Aug 4, 2024

Out-of-bounds write in Android kernel allows local users to escalate privileges via improper locking in the USB gadget endpoint queue. The __dwc3_gadget_ep0_queue function in ep0.c can write beyond bounds when locking is mishandled. Exploitation requires local access to an affected Android device, needs no additional execution privileges or user interaction, and can elevate privileges.

CVSS severity7.8
High
EPSS probability0.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Android kernel allows local users to escalate privileges via improper locking in the USB gadget endpoint queue. The __dwc3_gadget_ep0_queue function in ep0.c can write beyond bounds when locking is mishandled. Exploitation requires local access to an affected Android device, needs no additional execution privileges or user interaction, and can elevate privileges.

The record

CVE
CVE-2021-39640
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Android
Classifications
CWE-667, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=Android kernel

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Google Cloud · Androidversion=Android kernel

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NVDAV:L/AC:L/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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-667Improper Locking
T1068Exploitation for Privilege Escalation

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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