I recently wrote a diary on the SANS Internet Storm Center about revisiting the BrakTooth Bluetooth Classic vulnerability.

Please click here to read the full diary entry and this diary entry has been briefly mentioned in the SANS Daily Network Security Podcast (Stormcast) for Wednesday, November 3rd, 2021 over here . Alternatively, the full diary is reposted in full below.

I had previously written about the impacts and implications of BrakTooth in a previous diary [1]. As a brief recap, BrakTooth is a family of Bluetooth Classic vulnerabilities that were mainly caused by non-compliance to Bluetooth Core Specifications and their respective communication protocol layers. It has been about 2 months since BrakTooth was announced, so let us take a look at how things have progressed so far.

Affected vendors highlighted in the previous diary [1] have made some progress. With reference to Table 1 below, the summary of vulnerabilities, anomalies, devices and patch status are outlined (text in red are the changes since the previous diary entry).

SoC/Module VendorBluetooth SoCFirmware/
SDK Version
CVE/Anomaly (A)Patch Status
Espressif SystemsESP32esp-idf-4.4CVE-2021-28135
CVE-2021-28136
CVE-2021-28139

A1: Accepts lower Link Manager Protocol (LMP) length
Available [2], [3]
Infineon (Cypress)CYW20735B1WICED SDK 2.9.0CVE-2021-34145
CVE-2021-34146
CVE-2021-34147
CVE-2021-34148

A2: Accepts higher LMP length
A6: Ignore encryption stop
Available*
Bluetrum TechnologyAB5301AUnspecified (LMP Subver. 3)CVE-2021-34147
CVE-2021-34148

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Available*
IntelAX200Linux – ibt-12-16.ddc
Windows – 22.40.0
2 CVE IDs pending

A1: Accepts lower LMP length
A2: Accepts higher LMP length
A5: Invalid response
To be announced (TBA)
QualcommWCN3990crbtfw21.tlv, patch 0x0002CVE-2021-30348

A1: Accepts lower LMP length
A2: Accepts higher LMP length
A4: Ignore Role Switch Reject
TBA
Zhuhai Jieli TechnologyAC6366Cfw-AC63_BT_SDK 0.9.0CVE-2021-34143
CVE-2021-34144

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Available [4]
Zhuhai Jieli TechnologyAC6925CUnspecified (LMP Subver. 12576)CVE-2021-31611
CVE-2021-31613

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Investigation in progress
Zhuhai Jieli TechnologyAC6905XUnspecified (LMP Subver. 12576)CVE-2021-31611
CVE-2021-31612
CVE-2021-31613

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Investigation in progress
Actions TechnologyATS281XUnspecified (LMP Subver. 5200)CVE-2021-31717
CVE-2021-31785
CVE-2021-31786

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Investigation in progress
Harman InternationalJX25XUnspecified (LMP Subver. 5063)CVE-2021-28155

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Patch in progress
SilabsWT32iiWRAP 6.3.0 build 1149CVE-2021-31609

A1: Accepts lower LMP length
A2: Accepts higher LMP length
Investigation in progress
QualcommCSR8811/
CSR8510
v9.1.12.14CVE-2021-35093

A1: Accepts lower LMP length
A2: Accepts higher LMP length
No fix
Texas InstrumentsCC2564Ccc256xc_bt_sp_v1.4CVE-2021-34149

A1: Accepts lower LMP length
A2: Accepts higher LMP length
No fix

Table 1: Patch Status, Vulnerabilities and SDK?Firmware Version of Affected Devices (*Contact vendor to acquire patch)

The various patch statuses are explained as follows:

Available: The vendor has replicated the vulnerability and a patch is available.
To be announced (TBA): The vendor has produced a patch for internal testing and validation, but has yet to release such patch to the general public.
Patch in progress: The vendor has successfully replicated the vulnerability and a patch will be available soon.
Investigation in progress: The vendor is currently investigating the security issue and is being assisted by the researchers.
Pending: The vendor hardly communicated with the researchers and the status of their investigation is unclear at best. No patch is in pending state as of November 1st, 2021.
No fix: The vendor has successfully replicated the issue, but there is no plan to release a patch.

A new category – To be announced – was introduced as part of the classification of patch status. With reference to Table 1, Intel and Qualcomm had produced a patch for internal testing and validation, but had not released it to users. For AC6366C manufactured by Zhuhai Jieli Technology, a fix was made available. Meanwhile, a patch for JX25X from Harman International is being worked on. Finally, WT32i from Silabs is investigating the issue. In addition, three vendors (Samsung, Mediatek and Airoha) have independently tested their products and assessed that some of their products are affected by BrakTooth. However, the exact Bluetooth System-on-Chips (SoC) or firmware versions affected were not provided to the researchers.

Why is an update and retrospection of BrakTooth necessary? Previously, the Automated Systems SEcuriTy (ASSET) Research Group from Singapore University of Technology and Design (SUTD) had embargoed their Proof-of-Concept (PoC) code till October 31st, 2021. The PoC code has now been made available publicly, and thus could affect unpatched Bluetooth Classic devices. For end users and organizations, it is strongly recommended to update affected devices if a patch is available. For devices that have patches to be announced or in progress, it is highly recommended that users keep a close watch on the availability of the patches and apply them once they are available.

Users should also be cognizant of the possibility that other Bluetooth Classic products (other than the ones outlined in Table 1) could be affected by BrakTooth as the Bluetooth Classic stack is likely to be shared amongst many products. Prior recommendations suggested in my previous diary to identify, address and mitigate the risks of BrakTooth are still applicable [1].

References:
[1] https://isc.sans.edu/diary/27802
[2] https://www.espressif.com/sites/default/files/advisory_downloads/AR2021-004%20Bluetooth%20Security%20Advisory.pdf
[3] https://github.com/espressif/esp-idf/tree/bf71f494a165aba5e5365e17e1e258598d9fc172
[4] https://github.com/Jieli-Tech/fw-AC63_BT_SDK/commit/d1fdd03c167f416aaa5791b1325527791e0ab705

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