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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2021-37577

MEDIUM · 6.8 CVSS v3.1 Published 2024-10-01
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated

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 · unedited
Bluetooth LE and BR/EDR Secure Connections pairing and Secure Simple Pairing using the Passkey entry protocol in Bluetooth Core Specifications 2.1 through 5.3 may permit an unauthenticated man-in-the-middle attacker to identify the Passkey used during pairing by reflection of a crafted public key with the same X coordinate as the offered public key and by reflection of the authentication evidence of the initiating device, potentially permitting this attacker to complete authenticated pairing with the responding device using the correct Passkey for the pairing session. This is a related issue to CVE-2020-26558.

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 confidence

A vulnerability in the Passkey entry protocol for Bluetooth LE and BR/EDR Secure Connections pairing (specifications 2.1-5.3) allows an unauthenticated MITM attacker to identify the Passkey by reflecting a crafted public key with the same X coordinate as the offered public key and by reflecting the authentication evidence of the initiating device, enabling the attacker to complete authenticated pairing with the responding device.

MitigationThis is a specification-level vulnerability requiring updates to Bluetooth firmware and stack implementations from affected vendors. Users should ensure Bluetooth implementations are patched and exercise caution with pairing requests in untrusted environments.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS 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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:L

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Bluetooth implementation version
    Check the device's Bluetooth firmware or stack version. On Linux, use 'hciconfig -a' or check '/sys/class/bluetooth/hci0/version'. On Windows, check Device Manager > Bluetooth radio properties. On macOS, use 'system_profiler SPBluetoothDataType'.
    Affected if The Bluetooth implementation is from a vendor that has not released patches for CVE-2021-37577 and supports Bluetooth Core Specification versions 2.1 through 5.3 with Passkey entry pairing enabled.
  2. Confirm Passkey entry pairing is supported
    Check if the device supports Passkey entry as an authentication method. This can be verified by reviewing the Bluetooth settings or pairing capabilities. On Linux, 'bluetoothctl show' may display pairing methods. On mobile devices, check Bluetooth settings for passkey options.
    Affected if Passkey (or PIN-based) entry pairing is enabled or available on the device, as this is the specific protocol affected by the vulnerability.
  3. Verify vendor patch status
    Check the Bluetooth chipset or host stack vendor's security advisories, firmware release notes, or support documentation for CVE-2021-37577. Look for mentions of the Passkey MITM vulnerability fix in Bluetooth firmware or stack updates.
    Affected if The installed Bluetooth firmware or stack version predates the vendor's patch for this vulnerability and the device supports Passkey entry pairing.
  4. Assess pairing exposure
    Review whether the device is used or expected to pair with other devices in environments where an unauthenticated MITM attack is plausible (public or untrusted networks). Evaluate the pairing workflow and whether Passkey entry is commonly used.
    Affected if The device uses Passkey entry pairing in scenarios where an attacker could position themselves between two pairing devices.

A device is affected if it uses a Bluetooth implementation supporting Passkey entry pairing (Core Spec 2.1-5.3) that has not been patched by the vendor to address this MITM vulnerability in the Passkey entry protocol.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

This is a specification-level vulnerability requiring updates to Bluetooth firmware and stack implementations from affected vendors. Users should ensure Bluetooth implementations are patched and exercise caution with pairing requests in untrusted environments.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-37577 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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