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Ubuntu LinuxOperating system · Canonical

CVE-2019-9506

HIGH · 8.1 CVSS v3.1 Published 2019-08-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
86/100
Remediation priority · High
No privileges Zero-click

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
The Bluetooth BR/EDR specification up to and including version 5.1 permits sufficiently low encryption key length and does not prevent an attacker from influencing the key length negotiation. This allows practical brute-force attacks (aka "KNOB") that can decrypt traffic and inject arbitrary ciphertext without the victim noticing.

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 · high confidence

The KNOB attack exploits the Bluetooth BR/EDR specification (up to v5.1) by allowing attackers to manipulate the encryption key length negotiation, forcing the use of very low-entropy keys (even 1 byte of entropy). Attackers can then perform practical brute-force attacks to decrypt traffic and inject malicious ciphertext without detection by the victim.

MitigationApply vendor-provided firmware and software updates from Bluetooth chip manufacturers and device OEMs that address the KNOB attack. Ensure Bluetooth devices are running patched versions of the specification (Bluetooth Core Specification 5.1 and later require minimum 7 bytes of entropy).

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
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04= 19.04
Debian LinuxOperating system
Affected:= 8.0
Mrg RealtimeApplication
Affected:= 2.0
Virtualization Host EusApplication
Affected:= 4.2
Enterprise LinuxOperating system
Affected:= 8.0
Enterprise Linux AusOperating system
Affected:= 7.5
Enterprise Linux EusOperating system
Affected:= 7.6= 7.7= 8.1= 8.2= 8.4
Enterprise Linux For Real TimeOperating system
Affected:= 7= 8

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:A/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 checks

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

  1. Identify the operating system version
    Run 'cat /etc/os-release' or 'lsb_release -a' to determine the exact OS version and compare to the affected list: Ubuntu 16.04, 18.04, 19.04; Debian 8.0; Red Hat Enterprise Linux 7.x, 8.x, 8.0, 8.1, 8.2, 8.4; Red Hat MRG Realtime 2.0; Red Hat Virtualization Host 4.2
    Affected if The OS version matches one of the listed affected versions
  2. Verify Bluetooth hardware and software stack presence
    Run 'hciconfig -a' to list Bluetooth adapters, or check if the 'bluetooth' service is present via 'systemctl list-unit-files | grep bluetooth'
    Affected if Bluetooth hardware and the BlueZ stack are present on the system
  3. Check the BlueZ version
    Run 'bluetoothd --version' or 'dpkg -l | grep bluez' (Debian/Ubuntu) or 'rpm -qa | grep bluez' (Red Hat) to obtain the BlueZ daemon version
    Affected if The BlueZ version is older than the patches that enforce minimum 7-byte entropy (typically versions prior to BlueZ 5.50+)
  4. Determine if Bluetooth BR/EDR (Classic Bluetooth) is enabled
    Run 'hciconfig' to see adapter status; run 'hciconfig hci0 auth' to check authentication settings; check 'rfcomm' or 'bt-adapter --set Mode' output for BR/EDR configuration
    Affected if Bluetooth BR/EDR mode is active and encryption key negotiation can occur with unpatched devices
  5. Inspect Bluetooth pairing and encryption configuration
    Review '/var/lib/bluetooth/' or run 'bt-device --list' to see paired devices; check if 'EncryptionMode' is set to 'encrypt' in Bluetooth configuration files
    Affected if The system uses Bluetooth encryption without the enforced minimum key entropy from the specification update

The system is affected if it runs an affected OS version with an unpatched BlueZ stack and has Bluetooth BR/EDR enabled, allowing attackers to force low-entropy encryption keys during pairing.

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

Apply vendor-provided firmware and software updates from Bluetooth chip manufacturers and device OEMs that address the KNOB attack. Ensure Bluetooth devices are running patched versions of the specification (Bluetooth Core Specification 5.1 and later require minimum 7 bytes of entropy).

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation8.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,240
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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-2019-9506 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data