PSIRTCVE-2019-9506 Encryption Key Negotiation of Bluetooth (KNOB) Vulnerability
Summary
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.
This vulnerability only affects Bluetooth BR/EDR mode (aka. Classic mode), and does not impact Bluetooth LE mode (aka. BLE, Smart mode)
Affected Products
FortiOS is not impacted
FortiAP is not impacted
FortiAnalyzer is not impacted
FortiManager is not impacted
FortiSwitch below 6.4.0 is impacted (*)
* only FortiSwitch 424E, 426E and 448E series models under 6.0.x and 6.2.x and when their bluetooth feature been enabled and used then impacted.
Solutions
Upgrade to FortiSwitch 6.4.0
Starting from FortiSwitch 6.4.0, a new CLI option "min-key-length" was added:
config system bluetooth
set min-key-length [length] /* default length value is 7, allow 1 to 16 */
end
system will check the "pin" length based on min-key-length setting.
Workaround:
For FortiSwitch below 6.4.0, ensure the Bluetooth pair pin length is at least 7 characters:
config system bluetooth
set pin xxxxxxx /* ensure pin length >= 7 characters */
end
Revision History:
2020-04-17 Initial Version
2020-04-23 Detail the FortiSwitch impact models and condition.