dbcve.org
Ios XeOperating system · Cisco

CVE-2016-6386

HIGH · 7.5 CVSS v3.0 Published 2016-10-05
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
Cisco IOS XE 3.1 through 3.17 and 16.1 on 64-bit platforms allows remote attackers to cause a denial of service (data-structure corruption and device reload) via fragmented IPv4 packets, aka Bug ID CSCux66005.

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 versions 3.1-3.17 and 16.1 on 64-bit platforms allows remote attackers to send specifically crafted fragmented IPv4 packets that cause data-structure corruption, leading to device reload and denial of service. The vulnerability is exploitable remotely without authentication.

MitigationApply the appropriate Cisco IOS XE software update or implement network-level filtering of fragmented IPv4 packets at perimeter devices to block malicious fragmented traffic.

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:= 3.1.0s= 3.1.0sg= 3.1.1s= 3.1.1sg= 3.1.2s= 3.1.3as= 3.1.4as= 3.1.4s= 3.2.0se= 3.2.1s= 3.2.1se= 3.2.2s
Ios Xe 16.1Operating system
Affected:= 16.1.2
Ios Xe 3.2jaOperating system
Affected:= 3.2.0ja
Ios Xe 3.3sgOperating system
Affected:= 3.3.0sg= 3.3.1sg= 3.3.2sg
Ios Xe 3.3xoOperating system
Affected:= 3.3.0xo= 3.3.1xo= 3.3.2xo
Ios Xe 3.4sgOperating system
Affected:= 3.4.0sg= 3.4.1sg= 3.4.2sg= 3.4.3sg= 3.4.4sg= 3.4.5sg= 3.4.6sg= 3.4.7sg

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 Cisco IOS XE version
    Execute 'show version' or 'show version | include Version' on the device CLI to retrieve the installed IOS XE version number
    Affected if The displayed version matches any of the following: 3.1.0s, 3.1.0sg, 3.1.1s, 3.1.1sg, 3.1.2s, 3.1.3as, 3.1.4as, 3.1.4s, 3.2.0se, 3.2.1s, 3.2.1se, 3.2.2s, 16.1.2, 3.2.0ja, 3.3.0sg, 3.3.1sg, 3.3.2sg, 3.3.0xo, 3.3.1xo, 3.3.2xo, 3.4.0sg, 3.4.1sg, 3.4.2sg, 3.4.3sg, 3.4.4sg, 3.4.5sg, 3.4.6sg, or 3.4.7sg (
  2. Confirm the hardware platform is 64-bit
    Execute 'show version' and look for the platform type in the output; 64-bit platforms typically include ASR 1000 series, ISR 4000 series, or similar high-end routers
    Affected if The device is a 64-bit Cisco platform running the affected IOS XE versions listed above
  3. Verify IPv4 fragmentation processing is enabled
    Check the device configuration with 'show running-config | include ip frag' or 'show ip interface' to see if IPv4 fragmentation handling is active on any interface
    Affected if IPv4 fragmentation processing is enabled on any interface (this is the default behavior; the vulnerability triggers when the device processes fragmented IPv4 packets)
  4. Check for recent unexpected device reloads
    Review logs with 'show log' or 'show reload' and look for unexplained system crashes or reload events that occurred without admin intervention
    Affected if The device has experienced unexplained reloads or crashes, which could indicate exploitation attempts

The environment is affected if the device runs Cisco IOS XE version 3.1 through 3.17 or 16.1 on a 64-bit platform and IPv4 fragmentation is enabled, which is the default configuration.

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 the appropriate Cisco IOS XE software update or implement network-level filtering of fragmented IPv4 packets at perimeter devices to block malicious fragmented traffic.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation8.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,680
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $9,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2016-6386 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2016-6386 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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