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Ios XeOperating system · Cisco

CVE-2016-6438

MEDIUM · 5.9 CVSS v3.0 Published 2016-10-27
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
A vulnerability in Cisco IOS XE Software running on Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, remote attacker to cause a configuration integrity change to the vty line configuration on an affected device. This vulnerability affects the following releases of Cisco IOS XE Software running on Cisco cBR-8 Converged Broadband Routers: All 3.16S releases, All 3.17S releases, Release 3.18.0S, Release 3.18.1S, Release 3.18.0SP. More Information: CSCuz62815. Known Affected Releases: 15.5(3)S2.9, 15.6(2)SP. Known Fixed Releases: 15.6(1.7)SP1, 16.4(0.183), 16.5(0.1).

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 · high confidence

A vulnerability in Cisco IOS XE Software on cBR-8 Converged Broadband Routers allows an unauthenticated, remote attacker to modify the vty (virtual terminal) line configuration on affected devices. This configuration integrity change could enable unauthorized access to the device.

MitigationUpgrade Cisco IOS XE Software on cBR-8 routers to a fixed release (15.6(1.7)SP1, 16.4(0.183), 16.5(0.1) or later). If immediate upgrade is not possible, monitor vty configuration for unauthorized changes and restrict management plane exposure to trusted networks.

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
Ios XeOperating system
Affected:= 3.16.0cs= 3.16.0s= 3.16.1as= 3.16.1s= 3.16.2as= 3.16.2bs= 3.16.2s= 3.16.3as= 3.16.3s= 3.16.4s= 3.17.0s= 3.17.1as

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
None
Integrity
High
Availability
None

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/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. Identify device model
    Run 'show version' or 'show platform' command and look for 'cBR-8' or 'Converged Broadband Router' in the output
    Affected if Device is a Cisco cBR-8 Converged Broadband Router
  2. Check IOS XE version
    Run 'show version' and locate the 'IOS XE Software' version string (for example, 3.16.xs)
    Affected if Version matches any of these: 3.16.0cs, 3.16.0s, 3.16.1as, 3.16.1s, 3.16.2as, 3.16.2bs, 3.16.2s, 3.16.3as, 3.16.3s, 3.16.4s, 3.17.0s, or 3.17.1as
  3. Examine vty line configuration
    Run 'show running-config | include line vty' or 'show line vty' to view current vty line settings
    Affected if vty lines 0 4 (or similar range) are present in the configuration and the device is reachable over the network
  4. Verify vty configuration integrity
    Compare current vty configuration against a known-good baseline or check for unauthorized changes such as new access-class entries, added transport inputs, or altered login authentication
    Affected if Configuration differs from the expected baseline or shows unexpected modifications to vty line settings

The device is affected if it is a cBR-8 router running IOS XE version 3.16.0cs through 3.17.1as and has vty lines configured that could be remotely modified.

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

Upgrade Cisco IOS XE Software on cBR-8 routers to a fixed release (15.6(1.7)SP1, 16.4(0.183), 16.5(0.1) or later). If immediate upgrade is not possible, monitor vty configuration for unauthorized changes and restrict management plane exposure to trusted networks.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2016-6438 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data