CVE-2021-38786
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 · uneditedThere is a NULL pointer dereference in media/libcedarc/vdecoder of Allwinner R818 SoC Android Q SDK V1.0, which could cause a media crash (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 · moderate confidenceA NULL pointer dereference vulnerability exists in the media/libcedarc/vdecoder component of the Allwinner R818 SoC Android Q SDK V1.0. When processing media streams, the vdecoder fails to properly validate pointer allocations before dereferencing them, leading to a kernel or userspace crash resulting in denial of service.
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= 1.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify the SoC modelCheck /proc/cpuinfo or device tree for the system-on-chip identifier. Look for 'R818' or 'Allwinner R818' in the hardware information.Affected if The system is not based on the Allwinner R818 SoC, then this specific vulnerability does not apply.
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Confirm the Android SDK versionCheck the system build properties: /system/build.prop or /vendor/build.prop. Look for the SDK version and build identifier. The affected version is Android Q SDK = 1.0.Affected if The SDK version is not exactly 1.0, the specific vulnerability path may not exist.
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Verify libcedarc component presenceCheck if the libcedarc library is present on the system. Search in /vendor/lib/ or /system/lib/ for libcedarc.so. Also check /vendor/etc/ for any cedarc configuration files.Affected if The libcedarc library is not installed on the device, the vdecoder component for this vulnerability does not exist.
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Check if vdecoder is in useMonitor media decoding activity during media playback or encoding operations. Use 'ps -A' or check /proc/<pid>/maps to see if processes are linked against libcedarc. The vulnerability triggers when vdecoder processes media streams.Affected if The vdecoder component is never invoked (no media decoding occurs), the NULL dereference path is not triggered.
A system is affected if it uses the Allwinner R818 SoC with Android Q SDK version 1.0 and utilizes the libcedarc vdecoder component for media stream processing.
Generated from the published advisory. Verify against your own configuration.
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 dataThe vulnerability requires a code-level fix in the libcedarc vdecoder component - developers must add proper NULL pointer validation checks before dereferencing pointers in all media decoding paths, followed by graceful error handling for allocation failures.
- Consultation3.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-38786 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-38786 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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