CVE-2016-4521

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.

Published: 2016-05-31 Last update: 2026-05-06 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2016-4521 is rated Moderate Risk (58.8/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.41%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2016-4521

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 1.27% 0.41% -0.86%
2 2025-03-29 0.41% 1.27% +0.86%
3 2025-03-17 — 0.41% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2016-4521

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.0 CRITICAL
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
10.0 2.0 HIGH
AV:N/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 10.0 [email protected]

Weakness enumeration for CVE-2016-4521

Affected software / configurations for CVE-2016-4521

Vendor Product Version Raw CPE
sixnet bt-5_series_cellular_router_firmware <= 3.8.20 cpe:2.3:o:sixnet:bt-5_series_cellular_router_firmware:*:*:*:*:*:*:*:*
sixnet bt-5_series_cellular_router_firmware <= 3.9.7 cpe:2.3:o:sixnet:bt-5_series_cellular_router_firmware:*:*:*:*:*:*:*:*
sixnet bt-6_series_cellular_router_firmware <= 3.8.20 cpe:2.3:o:sixnet:bt-6_series_cellular_router_firmware:*:*:*:*:*:*:*:*
sixnet bt-6_series_cellular_router_firmware <= 3.9.7 cpe:2.3:o:sixnet:bt-6_series_cellular_router_firmware:*:*:*:*:*:*:*:*

References for CVE-2016-4521

URL Tags
https://ics-cert.us-cert.gov/advisories/ICSA-16-147-02 Third Party Advisory US Government Resource
cvelogic Threat Intelligence