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 Vendor | Bluetooth SoC | Firmware/ SDK Version | CVE/Anomaly (A) | Patch Status |
|---|---|---|---|---|
| Espressif Systems | ESP32 | esp-idf-4.4 | CVE-2021-28135 CVE-2021-28136 CVE-2021-28139 A1: Accepts lower Link Manager Protocol (LMP) length | Available [2], [3] |
| Infineon (Cypress) | CYW20735B1 | WICED SDK 2.9.0 | CVE-2021-34145 CVE-2021-34146 CVE-2021-34147 CVE-2021-34148 A2: Accepts higher LMP length A6: Ignore encryption stop | Available* |
| Bluetrum Technology | AB5301A | Unspecified (LMP Subver. 3) | CVE-2021-34147 CVE-2021-34148 A1: Accepts lower LMP length A2: Accepts higher LMP length | Available* |
| Intel | AX200 | Linux – 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) |
| Qualcomm | WCN3990 | crbtfw21.tlv, patch 0x0002 | CVE-2021-30348 A1: Accepts lower LMP length A2: Accepts higher LMP length A4: Ignore Role Switch Reject | TBA |
| Zhuhai Jieli Technology | AC6366C | fw-AC63_BT_SDK 0.9.0 | CVE-2021-34143 CVE-2021-34144 A1: Accepts lower LMP length A2: Accepts higher LMP length | Available [4] |
| Zhuhai Jieli Technology | AC6925C | Unspecified (LMP Subver. 12576) | CVE-2021-31611 CVE-2021-31613 A1: Accepts lower LMP length A2: Accepts higher LMP length | Investigation in progress |
| Zhuhai Jieli Technology | AC6905X | Unspecified (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 Technology | ATS281X | Unspecified (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 International | JX25X | Unspecified (LMP Subver. 5063) | CVE-2021-28155 A1: Accepts lower LMP length A2: Accepts higher LMP length | Patch in progress |
| Silabs | WT32i | iWRAP 6.3.0 build 1149 | CVE-2021-31609 A1: Accepts lower LMP length A2: Accepts higher LMP length | Investigation in progress |
| Qualcomm | CSR8811/ CSR8510 | v9.1.12.14 | CVE-2021-35093 A1: Accepts lower LMP length A2: Accepts higher LMP length | No fix |
| Texas Instruments | CC2564C | cc256xc_bt_sp_v1.4 | CVE-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