CVE-2021-35951: fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows an Unauthenticated Remote attacker to send a m

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HIGH 7.5REMOTEMITIGATE

CVE-2021-35951 is a high-severity flaw (CVSS 7.5) affecting reflex 2.0 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows an Unauthenticated Remote attacker to send a malicious firmware update via BLE and brick the device.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 39%)
CISA exploited list	No
Published	2022-12-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fastrack

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-12-26 06:15 UTCPublished CVE record published
2026-06-17 03:57 UTCUpdated Record last modified

fastrack reflex 2.0 firmware MITIGATE

Affected: 90.89

Fixed in: no fixed release known

Safe to downgrade to: a release before 90.89

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-35951?

reflex 2.0 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-35951 being exploited?

CVE-2021-35951 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-35951 affect?

CVE-2021-35951 affects reflex 2.0 firmware. Severity is high (CVSS 7.5). fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows an Unauthenticated Remote attacker to send a malicious firmware update via BLE and brick the device.

How urgent is CVE-2021-35951?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-35954 HIGH 8.1 MITIGATE fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows physically proximate attackers to dump the fir
CVE-2021-35953 HIGH 7.5 MITIGATE fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows a Remote attacker to cause a Denial of Service
CVE-2021-35952 MEDIUM 5.3 MITIGATE fastrack Reflex 2.0 W307S_REFLEX_v90.89 Activity Tracker allows a Remote attacker to change the time, date, an

References

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