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AndroidOperating system · Google

CVE-2021-0942

CRITICAL · 9.8 CVSS v3.1 Published 2022-09-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The path in this case is a little bit convoluted. The end result is that via an ioctl an untrusted app can control the ui32PageIndex offset in the expression:sPA.uiAddr = page_to_phys(psOSPageArrayData->pagearray[ui32PageIndex]);With the current PoC this crashes as an OOB read. However, given that the OOB read value is ending up as the address field of a struct I think i seems plausible that this could lead to an OOB write if the attacker is able to cause the OOB read to pull an interesting kernel address. Regardless if this is a read or write, it is a High severity issue in the kernel.Product: AndroidVersions: Android SoCAndroid ID: A-238904312

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A kernel vulnerability in Android allows an untrusted application to control the ui32PageIndex offset in a page_to_phys() expression via an ioctl, resulting in an out-of-bounds read from the pagearray. The OOB read value is used as an address field in a struct, potentially enabling OOB write if an attacker can control the leaked kernel address.

MitigationApply the vendor-provided Android kernel security patch for CVE-2021-0942 to address the missing bounds validation on ui32PageIndex in the affected driver.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AndroidOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the running Android kernel version
    Run 'cat /proc/version' or 'uname -a' to retrieve the kernel version string
    Affected if The kernel version is earlier than the version that includes the CVE-2021-0942 security patch; since all versions are listed as affected, any unpatched kernel version is potentially vulnerable
  2. Determine if the kernel has received the CVE-2021-0942 patch
    Check the kernel security patch level by reviewing the Android Security Bulletin for your Android version, or check the kernel configuration file for the specific bounds-checking fix if accessible
    Affected if The kernel security patch level is older than the month the CVE-2021-0942 fix was released (typically bundled in Android security updates)
  3. Identify drivers that expose ioctl interfaces with ui32PageIndex
    Examine loaded kernel modules with 'lsmod' and review any custom or vendor-specific drivers that handle ioctl calls related to memory paging or physical page operations
    Affected if A driver that handles page_to_phys() operations with user-controlled ui32PageIndex via ioctl is loaded and accessible to untrusted applications

A device is affected if it runs an unpatched Android kernel where the specific driver with the vulnerable ui32PageIndex ioctl handling is present and exposed to untrusted applications.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-provided Android kernel security patch for CVE-2021-0942 to address the missing bounds validation on ui32PageIndex in the affected driver.

Recommended fix Moderate confidence

January 2022 Android Security Patch Level (SPL) or later - typically bundled with Android 12 or later kernel updates

  1. 1. Check the Android Security Bulletin for the month this CVE was addressed (CVE-2021-0942 was addressed in the January 2022 Android Security Bulletin)
  2. 2. Apply the January 2022 Android Security Patch Level (SPL) or later to your device
  3. 3. Verify the patch is applied by checking Settings > About Phone > Android version - it should show the January 2022 security patch or later
  4. 4. If your device manufacturer has not released an update, consider upgrading to a device that receives regular security updates
  5. 5. As a mitigation, avoid installing apps from untrusted sources to reduce the attack surface for this privilege escalation vulnerability
Caveat Applying major Android version updates to receive security patches may change device behavior; ensure backups before updating

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Android Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA6.0 h
32.0 hours of engineering $5,520
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-0942 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data