CVE-2021-31609
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 · uneditedThe Bluetooth Classic implementation in Silicon Labs iWRAP 6.3.0 and earlier does not properly handle the reception of an oversized LMP packet greater than 17 bytes, allowing attackers in radio range to trigger a crash in WT32i via a crafted LMP packet.
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 confidenceThe Bluetooth Classic implementation in Silicon Labs iWRAP 6.3.0 and earlier fails to properly handle LMP (Link Manager Protocol) packets exceeding 17 bytes, allowing adjacent attackers within radio range to send crafted malicious LMP packets that cause a crash (Denial of Service) on WT32i devices.
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<= 6.3.0CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:A/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 if the device runs Silicon Labs iWRAP firmwareCheck the device documentation, firmware build information, or system logs for 'iWRAP' or 'WT32i' branding. Consult the module label or product specifications if physically accessible.Affected if The device is confirmed to be a Silicon Labs iWRAP-based module, particularly the WT32i variant.
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Determine the installed iWRAP firmware versionAccess the device configuration interface or firmware management system and retrieve the iWRAP firmware version string. This is typically displayed in boot logs, firmware info commands, or the module's AT+I command output.Affected if The firmware version is 6.3.0 or any earlier version (e.g., 6.2.x, 6.1.x, etc.).
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Confirm Bluetooth Classic (BR/EDR) is enabledCheck the device's Bluetooth configuration settings or runtime status to verify that Classic Bluetooth (not Bluetooth Low Energy only) is active and accepting connections.Affected if Bluetooth Classic mode is enabled; the vulnerability affects LMP handling in Classic Bluetooth, not LE.
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Verify the device is operating within radio range of potential attackersAssess the physical deployment environment. Determine if the device is in a location where untrusted adjacent attackers could be within the standard Bluetooth range (typically 10-100 meters).Affected if The device accepts Classic Bluetooth connections from untrusted adjacent devices without additional radio shielding or physical access controls.
A user is affected if the device runs iWRAP firmware version 6.3.0 or earlier AND has Bluetooth Classic enabled, making it susceptible to crafted LMP packets from nearby attackers.
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 dataUpdate iWRAP firmware to a patched version if available from Silicon Labs; if no patch exists, consider replacing affected WT32i modules with newer Bluetooth hardware that receives security updates.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31609 — 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-2021-31609 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
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