CVE-2021-0938

Local information disclosure via optimized-away zeroing

Published Oct 25, 2021 · Updated Aug 3, 2024

Android kernel information disclosure before the relevant compiler fix allows local users to read residual memory through memzero_explicit. The compiler-clang.h implementation omitted barrier_data(), allowing Clang to optimize a zeroing call away and leave sensitive data uninitialized. Exploitation requires local code execution with low privileges and no user interaction; impact is confined to confidentiality.

CVSS severity5.5
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Android kernel information disclosure before the relevant compiler fix allows local users to read residual memory through memzero_explicit. The compiler-clang.h implementation omitted barrier_data(), allowing Clang to optimize a zeroing call away and leave sensitive data uninitialized. Exploitation requires local code execution with low privileges and no user interaction; impact is confined to confidentiality.

The record

CVE
CVE-2021-0938
Published
Oct 25, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Android
Classifications
CWE-908, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 25, 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?

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  1. Affected versionversion=Android kernel

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Google Cloud · Androidversion=Android kernel

Published CVSS scores

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

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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