CVE-2021-39741
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 · uneditedIn Keymaster, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-12LAndroid ID: A-173567719
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 missing bounds check in Android's Keymaster component allows an out-of-bounds write, enabling local privilege escalation from System privileges. This is a memory corruption vulnerability in the key management subsystem that does not require user interaction.
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= 12.1CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 checksWork through these to decide whether this CVE applies to you.
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Verify Android versionCheck the device settings under Settings > About Phone > Android version, or run 'getprop ro.build.version.release' via ADB shellAffected if Version displays as 12.1 (specifically Android 12, not 12L or later)
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Check security patch levelRun 'getprop ro.build.version.security_patch' via ADB shell or check Settings > About Phone > Security patch levelAffected if The patch level is earlier than the Android-12L security patch (date before March 2022) or shows as unpatched
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Confirm Keymaster hardware-backed key store is presentRun 'keymaster_hal' or check /vendor/lib/hw/keymaster*.so existence, or verify via 'dumpsys keymaster' command outputAffected if Keymaster HAL is present and responding (vulnerability requires this component to be exploitable)
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Verify system-level access contextRun 'id' command via ADB shell to check process privilegesAffected if Process or shell has System user privileges (UID 1000) or root (UID 0), as exploitation requires escalation from System to root
Affected if running Android 12.1 without the Android-12L security patch and the device has Keymaster hardware-backed key management enabled
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.
dbcve · scopedApply the Android-12L security patch that addresses the missing bounds check in Keymaster. Given this is a hardware-backed security component, ensure the patch is validated through Android compatibility testing.
Android 12L with January 2022 security update or Android 13+
- Upgrade the device to Android 12L with the January 2022 security patch level or later
- Alternatively, upgrade to Android 13 or later which contains the fix
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39741 — 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-2021-39741 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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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.
- 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