dbcve.org
Android Q SdkApplication · Allwinnertech

CVE-2021-38788

HIGH · 7.5 CVSS v3.1 Published 2022-01-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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 Background service in Allwinner R818 SoC Android Q SDK V1.0 is used to manage background applications. Malicious apps can use the interface provided by the service to set the number of applications allowed to run in the background to 0 and add themselves to the whitelist, so that once other applications enter the background, they will be forcibly stopped by the system, causing a denial of service.

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

The Background service in Allwinner R818 SoC Android Q SDK V1.0 lacks proper authorization checks on its interface, allowing any installed application to set the maximum background app count to 0 and add itself to a whitelist. This causes the system to forcibly terminate all non-whitelisted applications when they enter the background state, resulting in denial of service for legitimate apps.

MitigationThe service interface should enforce proper permission checks (e.g., signature or system-level permissions) to restrict modification of background app limits and whitelist management to privileged system components only, preventing untrusted applications from abusing these functions.

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
Android Q SdkApplication
Affected:= 1.0

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 SoC hardware
    Check /proc/cpuinfo or use 'getprop ro.hardware' to confirm the device uses the Allwinner R818 SoC
    Affected if The hardware is not Allwinner R818 (unaffected)
  2. Verify Android SDK version
    Use 'getprop ro.build.version.sdk' and check for a custom Allwinner SDK version property (often in 'getprop ro.build.version.allwinner' or similar) indicating Android Q SDK V1.0
    Affected if SDK is not Android Q SDK V1.0 (unaffected)
  3. Locate the Background service
    Check for the Allwinner background service process or daemon (often named 'backgroundservice', 'bgd', or similar in /system/bin or /vendor/bin) and confirm it is running via 'ps -A | grep -i background'
    Affected if The Background service is not present or not running (unaffected)
  4. Inspect Background service permissions
    Check the service's SELinux domain and Android permissions in /sepolicy or service definitions in /system/etc/permissions. Look for any signature or system-level permission requirements on the interface
    Affected if The service has no signature/system permission enforcement on its interface (likely affected)
  5. Review whitelist configuration
    Examine the Background service configuration files (typically in /data/system or /system/etc) for whitelist entries using 'grep -r whitelist /data/system/' or similar paths. Check if any untrusted (non-system) UIDs are whitelisted
    Affected if Non-system applications appear in the whitelist or max background count is set to 0 (likely affected)
  6. Monitor for app termination patterns
    Check logcat or dmesg for patterns of 'Force stopping' or app termination messages that correlate with apps entering background state, especially for non-whitelisted apps
    Affected if Legitimate apps are being forcibly terminated when entering background (confirmed exploitation)

A defender is affected if their device runs Allwinner R818 SoC with Android Q SDK V1.0, the Background service is present, and the service lacks proper permission checks allowing any app to manipulate the background limit and whitelist.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

The service interface should enforce proper permission checks (e.g., signature or system-level permissions) to restrict modification of background app limits and whitelist management to privileged system components only, preventing untrusted applications from abusing these functions.

Fix this in Android Q Sdk Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2021-38788 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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