CVE-2021-39736

Local privilege escalation via integer-overflowed buffer writes

Published Mar 16, 2022 · Updated Aug 4, 2024

Out-of-bounds writes in the Android kernel allow local users with System execution privileges to escalate privileges without user interaction. The prepare_io_entry and prepare_response paths in lwis_ioctl.c and lwis_periodic_io.c permit an integer calculation to overflow before a buffer write, causing the write to exceed its intended bounds. Exploitation is local, requires System execution privileges, and elevates privileges on the affected device.

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

Out-of-bounds writes in the Android kernel allow local users with System execution privileges to escalate privileges without user interaction. The prepare_io_entry and prepare_response paths in lwis_ioctl.c and lwis_periodic_io.c permit an integer calculation to overflow before a buffer write, causing the write to exceed its intended bounds. Exploitation is local, requires System execution privileges, and elevates privileges on the affected device.

The record

CVE
CVE-2021-39736
Published
Mar 16, 2022
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Android
Classifications
CWE-787, CWE-190, 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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-190Integer Overflow or Wraparound
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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