CVE-2016-4521
No exploitation reported by the sources we read.
- Published2016-05-31
- WeaknessCWE-200
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
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.
Timeline
dates in UTC- 2016-05-3101:59CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2016-4521?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2016-4521?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.8 | ≤ 3.8.20 | no fix published | NVD |
| 3.9 | ≤ 3.9.7 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.8 | ≤ 3.8.20 | no fix published | NVD |
| 3.9 | ≤ 3.9.7 | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Distribution builds and vendor advisories
Packages from OSV.dev and products from the vendors' CSAF advisories.
version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.
Vendor advisories
Sixnet BT Series Hard-coded Credentials Vulnerability
Sixnet Sixnet BT-5xxx and BT-6xxx series M2M cellular routers: <3.8.21
Fix
- Mitigation from the vendor CISA ICSA-16-147-02 · 1 productSixnet has produced patches and new firmware (versions 3.8.21 or 3.9.8) to address this issue. Users are recommended to install the latest version. Firmware and release notes can be found on Sixnet’s software and firmware page at the following location: (http://www.redlion.net/resources/software/si…
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.09.8read 2026-10-23
- NVDCVSS 2.010read 2026-10-23
- NVDweakness (CWE)CWE-200read 2026-10-23
- FIRST EPSSEPSS score2.5 %2026-10-23
Technical details
- CVSS v3 Vector
- CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Published
- 2016-05-31
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2016-4521?
Is CVE-2016-4521 actively exploited?
What is the CVSS score for CVE-2016-4521?
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.