CVE-2021-39672
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 fastboot, there is a possible secure boot bypass due to a configuration error. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android SoC Android ID: A-202018701
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 confidenceIn fastboot, a bootloader protocol used for Android device flashing, there is a configuration error that allows secure boot bypass. This enables local privilege escalation without requiring user interaction or additional execution privileges, as the secure boot verification can be circumvented through the misconfigured fastboot implementation.
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 dataall versionsCVSS 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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Check bootloader lock statusRun 'fastboot oem device-info' or 'fastboot flashing get_unlock_ability' to query the bootloader lock state. A locked bootloader indicates secure boot verification is enforced.Affected if The bootloader is unlocked or the 'unlock_ability' is enabled, allowing unsigned images to be flashed via fastboot.
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Verify secure boot enforcement stateRun 'fastboot oem secure-boot' or check 'fastboot getvar secure_boot' if available on your device. This queries whether the device enforces secure boot verification.Affected if Secure boot is reported as disabled, bypassed, or not enforced, indicating the configuration error is present.
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Test fastboot signature verificationAttempt to flash an unsigned boot or recovery image using 'fastboot flash boot unsigned_image.img' (use a test image in a sandboxed environment). Observe if the flash operation succeeds despite the image being unsigned.Affected if The device accepts and flashes unsigned images through fastboot, confirming the bypass is possible.
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Check bootloader verification flagsRun 'fastboot getvar all' and examine fields like 'verified boot state', 'vbmeta', or 'verification enabled' to determine if cryptographic verification is active.Affected if Verification fields show disabled, permissive, or false, indicating the secure boot bypass condition exists.
The device is affected if the bootloader is unlocked, or if fastboot accepts unsigned images, or if secure boot verification is reported as disabled or bypassed.
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 dataCorrect the secure boot configuration in the bootloader/firmware to ensure proper verification is enforced. This typically requires updating the secure boot policy and re-signing the bootloader with proper cryptographic keys through the OEM or SoC vendor.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39672 — 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-2021-39672 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