CVE-2021-39733

Local privilege escalation via unchecked ioctl input

Published Mar 16, 2022 · Updated Aug 4, 2024

An out-of-bounds write in Android kernel Audio code allows local users with System privileges to elevate privileges without interaction. The amcs_cdev_unlocked_ioctl function in audiometrics.c inadequately validates ioctl input before writing beyond an intended buffer boundary. Exploitation requires existing System execution privileges on an affected Pixel device and can compromise kernel-controlled confidentiality, integrity, and availability.

CVSS severity6.7
Medium
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds write in Android kernel Audio code allows local users with System privileges to elevate privileges without interaction. The amcs_cdev_unlocked_ioctl function in audiometrics.c inadequately validates ioctl input before writing beyond an intended buffer boundary. Exploitation requires existing System execution privileges on an affected Pixel device and can compromise kernel-controlled confidentiality, integrity, and availability.

The record

CVE
CVE-2021-39733
Published
Mar 16, 2022
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Android
Classifications
CWE-787, T1404
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 16, 2022CVE 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 privilegesadmin

What is affected?

Google Cloud · Androidversion=Android kernel

Published CVSS scores

4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
6.7NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1404Exploitation 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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