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Ios XeOperating system · Cisco

CVE-2019-12647

HIGH · 7.5 CVSS v3.1 Published 2019-09-25
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
A vulnerability in the Ident protocol handler of Cisco IOS and IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability exists because the affected software incorrectly handles memory structures, leading to a NULL pointer dereference. An attacker could exploit this vulnerability by opening a TCP connection to specific ports and sending traffic over that connection. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.

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 NULL pointer dereference vulnerability exists in the Ident protocol handler of Cisco IOS and IOS XE Software. An unauthenticated remote attacker can exploit this by opening a TCP connection to specific ports and sending specially crafted traffic, causing the affected device to reload and result in a denial of service condition.

MitigationApply the appropriate Cisco IOS/IOS XE software update or use ACLs to block access to the Ident protocol ports (TCP port 113) from untrusted networks until the patch can be applied.

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:= fuji-16.7.1= fuji-16.8.1

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:3.1/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 device and version
    Log into the device and run 'show version' to display the Cisco IOS or IOS XE version information. Note the exact version number and train (e.g., 16.7.x, 16.8.x).
    Affected if The device runs Cisco IOS XE and the version falls within the Fuji 16.7.x or 16.8.x train.
  2. Check if Ident protocol is listening
    Run 'show tcp brief' or use 'show listeners' command to see if the device is listening on TCP port 113 (Ident protocol). Alternatively, scan the device from an external host using 'nmap -p 113 <device-ip>' to check if port 113 is open.
    Affected if Port 113/TCP is open and the device is accepting Ident protocol connections.
  3. Verify Ident protocol handler is enabled
    Check the device configuration for any 'ident' or 'ip ident' commands under the relevant interface or line configurations. Use 'show running-config | include ident' to search for Ident-related configuration.
    Affected if The Ident protocol handler is explicitly enabled in the device configuration.
  4. Assess network exposure
    Review inbound ACLs on external-facing interfaces to determine if TCP port 113 traffic from untrusted networks is permitted. Use 'show ip interface' and examine applied access-lists.
    Affected if TCP port 113 is reachable from untrusted or internet-facing networks without appropriate filtering.

A device is affected if it runs Cisco IOS XE Fuji 16.7.x or 16.8.x, has the Ident protocol (port 113) enabled and listening, and is exposed to untrusted network traffic on that port.

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/IOS XE software update or use ACLs to block access to the Ident protocol ports (TCP port 113) from untrusted networks until the patch can be applied.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,800
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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-2019-12647 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
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