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iOSOperating system · Cisco

CVE-2016-1409

HIGH · 7.5 CVSS v3.0 Published 2016-05-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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
The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in Cisco IOS XE 2.1 through 3.17S, IOS XR 2.0.0 through 5.3.2, and NX-OS allows remote attackers to cause a denial of service (packet-processing outage) via crafted ND messages, aka Bug ID CSCuz66542, as exploited in the wild in May 2016.

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

A vulnerability in the IPv6 Neighbor Discovery (ND) protocol implementation in Cisco IOS XE (versions 2.1-3.17S), IOS XR (versions 2.0.0-5.3.2), and NX-OS allows remote attackers to send crafted ND messages that cause a denial of service via packet-processing outage. This was actively exploited in the wild in May 2016.

MitigationApply Cisco security patches for the specific product lines (IOS XE, IOS XR, NX-OS) to address the ND protocol flaw; until patched, consider IPv6 access control lists or disabling IPv6 on untrusted interfaces to filter malicious ND messages.

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
iOSOperating system
Affected:= 12.0\(1\)= 12.0\(1\)db= 12.0\(1\)s= 12.0\(1\)t= 12.0\(1\)t1= 12.0\(1\)xa= 12.0\(1\)xa1= 12.0\(1\)xa2= 12.0\(1\)xa3= 12.0\(1\)xa4= 12.0\(1\)xb= 12.0\(1\)xb1
Ios XeOperating system
Affected:= 2.1.0= 2.1.1= 2.1.2= 2.1.3= 2.2.0= 2.2.1= 2.2.2= 2.2.3= 2.3.0= 2.3.0t= 2.3.1= 2.3.1t
Ios XrOperating system
Affected:= 2.0.0= 3.0.0= 3.0.1= 3.2.0= 3.2.1= 3.2.2= 3.2.3= 3.2.4= 3.2.6= 3.2.50= 3.3.0= 3.3.1
Nx OsOperating system
Affected:= 1.0\(1.110a\)= 1.0\(1e\)= 1.0\(2j\)= 1.1\(0.825a\)= 1.1\(1g\)= 4.0\(0\)n1\(1a\)= 4.0\(0\)n1\(2\)= 4.0\(0\)n1\(2a\)= 4.0\(1a\)n1\(1\)= 4.0\(1a\)n1\(1a\)= 4.0\(1a\)n2\(1\)= 4.0\(1a\)n2\(1a\)

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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 the device OS and version
    Run 'show version' on the device CLI to retrieve the IOS/IOS XE/IOS XR/NX-OS version string
    Affected if The version matches one listed in the affected versions for your product line
  2. Confirm IPv6 is enabled globally
    Run 'show ipv6 general-prefix' or 'show running-config | include ipv6' to check for IPv6 configuration
    Affected if IPv6 is configured or enabled on the device
  3. Check IPv6 interface configurations
    Run 'show ipv6 interface brief' to list all interfaces with IPv6 addresses
    Affected if Any interface has an IPv6 address assigned, indicating active IPv6 usage
  4. Verify ND protocol processing is active
    Run 'show ipv6 neighbors' to see cached ND entries, confirming the device is processing ND messages
    Affected if The neighbor cache contains entries, confirming ND is active

You are affected if your device runs a matching IOS XE, IOS XR, or NX-OS version from the list AND IPv6 is enabled on any interface, because the vulnerability triggers when crafted ND messages are processed.

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

Apply Cisco security patches for the specific product lines (IOS XE, IOS XR, NX-OS) to address the ND protocol flaw; until patched, consider IPv6 access control lists or disabling IPv6 on untrusted interfaces to filter malicious ND messages.

Fix this in iOS 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-2016-1409 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