CVE-2021-1638
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 · uneditedMicrosoft is aware of the "Impersonation in the Passkey Entry Protocol" vulnerability. For more information regarding the vulnerability, please see this statement from the Bluetooth SIG. To address the vulnerability, Microsoft has released a software update that will fail attempts to pair if the remote device exchanges a public key with the same X coordinate as the locally exchanged public key
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 confidenceThis is a Bluetooth Passkey Entry protocol vulnerability allowing impersonation attacks. An attacker could exploit the protocol by presenting a public key with the same X coordinate as the legitimate device's public key during pairing, potentially authenticating as the victim. Microsoft released an update that rejects pairing attempts when both parties exchange public keys with matching X coordinates.
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= 20h2= 1803= 1809= 1909= 2004= 20h2= 1909= 2004all 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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 Windows versionRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify the installed Windows version and build numberAffected if The version matches one of the affected releases: Windows 10 versions 1803, 1809, 1909, 2004, or 20h2; Windows Server 2016 versions 1909, 2004, or 20h2; or any version of Windows Server 2019
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Confirm Bluetooth hardware is presentOpen Device Manager, expand 'Bluetooth', or run 'Get-PnpDevice -Class Bluetooth' in PowerShell to list Bluetooth adaptersAffected if A Bluetooth adapter is listed and its driver is loaded, indicating the system has Bluetooth capability
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Check Bluetooth status and recent pairing activityRun 'netsh bluetooth show state' to see if Bluetooth is enabled, and check Event Viewer under 'Microsoft/Windows/Bluetooth' for pairing eventsAffected if Bluetooth is enabled and there are recent pairing events using Passkey Entry authentication method
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Identify pairing method usedReview pairing event logs in Event Viewer under 'Applications and Services Logs/Microsoft/Windows/Bluetooth/Operational' or inspect pairing history in Windows Settings under Bluetooth & devices > Devices > Device settingsAffected if Pairing was performed using Passkey Entry (numeric entry of a 6-digit code) rather than Just Works or other methods
A system is affected if it runs one of the listed vulnerable Windows versions, has Bluetooth enabled, and has performed pairing using the Passkey Entry protocol with a potentially compromised key exchange.
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 dataApply the Microsoft software update that fails pairing attempts when the remote device's public key X coordinate matches the locally generated public key's X coordinate.
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1638 — 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-2021-1638 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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- 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
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