CVE-2016-4521: Sixnet Bt-5 Series Cellular Router Firmware

Critical severity, CVSS 9.8. EPSS: 2.5% chance of exploitation in the next 30 days.

Sixnet BT-5xxx and BT-6xxx M2M devices before 3.8.21 and 3.9.x before 3.9.8 have hardcoded credentials, which allows remote attackers to obtain access via unspecified vectors.

Affected products

• Sixnet Bt-5 Series Cellular Router Firmware: up to and including 3.8.20; up to and including 3.9.7
• Sixnet Bt-6 Series Cellular Router Firmware: up to and including 3.8.20; up to and including 3.9.7

Published 2016-05-31. Last modified 2026-06-17.