dbcve.org
Nwa1100 N FirmwareOperating system · Zyxel

CVE-2015-7256

MEDIUM · 5.9 CVSS v3.0 Published 2017-09-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
ZyXEL NWA1100-N, NWA1100-NH, NWA1121-NI, NWA1123-AC, and NWA1123-NI access points; P-660HN-51, P-663HN-51, VMG1312-B10A, VMG1312-B30A, VMG1312-B30B, VMG4380-B10A, VMG8324-B10A, VMG8924-B10A, VMG8924-B30A, and VSG1435-B101 DSL CPEs; PMG5318-B20A GPONs; SBG3300-N000, SBG3300-NB00, and SBG3500-N000 small business gateways; GS1900-8 and GS1900-24 switches; and C1000Z, Q1000, FR1000Z, and P8702N project models use non-unique X.509 certificates and SSH host keys.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Multiple ZyXEL networking devices (access points, DSL CPEs, GPONs, switches, and project models) ship with pre-installed, non-unique X.509 certificates and SSH host keys that are identical across all devices of the same model. This allows attackers to potentially impersonate devices or conduct man-in-the-middle attacks since the same certificate/key can be reused across thousands of devices.

MitigationGenerate and deploy unique X.509 certificates and SSH host keys on affected devices. Contact ZyXEL for firmware updates that may address this issue.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nwa1100 N FirmwareOperating system
Affected:all versions
Nwa1100 Nh FirmwareOperating system
Affected:all versions
Nwa1121 Ni FirmwareOperating system
Affected:all versions
Nwa1123 Ac FirmwareOperating system
Affected:all versions
Nwa1123 Ni FirmwareOperating system
Affected:all versions
P 660hn 51 FirmwareOperating system
Affected:all versions
P 663hn 51 FirmwareOperating system
Affected:all versions
Vmg1312 B10a FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Retrieve the SSL certificate fingerprint from the device
    Run: openssl s_client -connect <deviceIP>:443 2>/dev/null | openssl x509 -noout -fingerprint
    Affected if The certificate fingerprint matches the default certificate known for that specific ZyXEL model, or matches the certificate from another device of the same model
  2. Extract the SSH host key from the device
    Run: ssh-keyscan -t rsa,dsa,ecdsa <deviceIP> to retrieve the SSH host key, or access the device filesystem via firmware extraction to read /etc/ssh/ssh_host_*
    Affected if The SSH host key matches the default key shipped with that specific ZyXEL model, or matches the key from another device of the same model
  3. Compare SSH host keys across multiple devices of the same model
    If you have two or more ZyXEL devices of the same model, run ssh-keyscan on each and compare the outputs directly
    Affected if Two or more devices of the same model return identical SSH host keys, indicating non-unique pre-installed keys
  4. Compare SSL certificates across devices of the same model
    Retrieve the certificate from each device using openssl s_client and compare the fingerprints: openssl s_client -connect <deviceIP>:443 2>/dev/null | openssl x509 -noout -fingerprint
    Affected if Two or more devices of the same model have identical certificate fingerprints, indicating reuse of the same pre-installed certificate

A device is affected if its SSH host key or X.509 certificate is identical to another device of the same model, meaning the default non-unique keys were never replaced.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Generate and deploy unique X.509 certificates and SSH host keys on affected devices. Contact ZyXEL for firmware updates that may address this issue.

Fix this in Nwa1100 N Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2015-7256 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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