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Advisory ID:               SYSS-2025-023
Product:                   COROS PACE 3; other models might also be affected [7]
Manufacturer:              COROS Wearables, Inc.
Affected Version(s):       <= V 3.1008.0
Tested Version(s):         V 3.0808.0
Vulnerability Type:        Use of a Broken or Risky Cryptographic Algorithm (CWE-327)
Risk Level:                Medium
Solution Status:           Fixed
Manufacturer Notification: 2025-03-14
Solution Date:             July/August (see vendor notes[7])
Public Disclosure:         2025-06-17
CVE Reference:             CVE-2025-32876
Author of Advisory:        Moritz Abrell, SySS GmbH

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Overview:

The COROS PACE 3 is a professional GPS sport smart watch.

The manufacturer describes the product as follows (see [1]):

"Improving on its legendary predecessor in every way, PACE 3 packs an 
even more powerful punch. Track your training and recovery with a watch 
that's lightweight and comfortable, with advanced technology, 
outstanding data accuracy, and backed by the industry-leading COROS 
training software system. The COROS PACE 3 paves the way to discover 
your potential."

Due to missing implemention of LE Secure Connections, the Bluetooth Low
Energy (BLE) communication is vulnerable to passive sniffing attacks. 

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Vulnerability Details:

The BLE implementation of the COROS smartwatch does not support 
LE Secure Connections and instead enforces BLE Legacy Pairing.
In BLE Legacy Pairing, the Short-Term Key (STK) can be easily guessed. 
This requires knowledge of the Temporary Key (TK), which, in the case 
of the COROS PACE 3, is set to "0" due to the "Just Works" 
pairing method (see SYSS-2025-024[2]).

An attacker within Bluetooth range can therefore perform sniffing 
attacks, allowing eavesdropping on the communication.

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Proof of Concept (PoC):

By establishing a connection to a COROS PACE 3 and initiating the 
pairing process while analyzing the Bluetooth communication—for example, 
using Wireshark—the following behavior can be observed:

SMP Pairing Request of a client:
    AuthReq: 
        00.. .... = Reserved: 0x0
        ..1. .... = CT2 Flag: True
        ...0 .... = Keypress Flag: False
        .... 1... = Secure Connection Flag: True
        .... .1.. = MITM Flag: True
        .... ..01 = Bonding Flags: Bonding (0x1)


SMP Pairing Response of the COROS PACE 3:
    AuthReq: 
        00.. .... = Reserved: 0x0
        ..0. .... = CT2 Flag: False
        ...0 .... = Keypress Flag: False
        .... 0... = Secure Connection Flag: False
        .... .0.. = MITM Flag: False
        .... ..01 = Bonding Flags: Bonding (0x1)

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Solution:

According to vendor note [7], the vulnerability was addressed in patches 
for several devices.

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Disclosure Timeline:

2025-03-10: Vulnerability discovered
2025-03-14: Vulnerability reported to manufacturer
2025-03-14: Confirmation of receipt received
2025-03-17: Asked the manufacturer for an update
2025-03-31: More information provided to the manufacturer
2025-04-07: Asked the manufacturer for an update
2025-04-14: Informed the manufacturer about the assigned CVE-ID and
            asked for an update once again
2025-04-15: Answer received from the manufacturer; manufacturer informed
            SySS GmbH that a fix for the vulnerability is planned for the
            end of the year (2025)
2025-04-15: Receipt confirmed, and the issue was clarified once more,
            along with a recommendation for prompt resolution
2025-06-17: Public disclosure
2025-08-06: The vendor notified us of updates to the security patch notes
2025-08-11: Advisory update

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References:

[1] COROS PACE 3 product website
    https://eu.coros.com/pace3
[2] SySS Security Advisory SYSS-2025-024
    https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2025-024.txt
[3] SySS Security Advisory SYSS-2025-023
    https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2025-023.txt
[4] SySS Responsible Disclosure Policy
    https://www.syss.de/en/responsible-disclosure-policy
[5] CVE-2025-32876
    https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-32876
[6] Detailed blog post:
    https://blog.syss.com/posts/bluetooth-analysis-coros-pace-3/
[7] Vendor notes about the vulnerability and security patches:
    https://support.coros.com/hc/en-us/articles/38933102526996-Bluetooth-Security-Vulnerability-Statement

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Credits:

This security vulnerability was found by Moritz Abrell of SySS GmbH.

E-Mail: moritz.abrell@syss.de
Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Moritz_Abrell.asc
Key Fingerprint: 2927 7EB6 1A20 0679 79E9  87E6 AE0C 9BF8 F134 8B53

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Disclaimer:

The information provided in this security advisory is provided "as is" 
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS website.

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Copyright:

Creative Commons - Attribution (by) - Version 3.0
URL: http://creativecommons.org/licenses/by/3.0/deed.en
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