dbcve.org
RemoteApplication · Cisco

CVE-2018-15391

HIGH · 7.5 CVSS v3.0 Published 2018-10-05
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
A vulnerability in certain IPv4 fragment-processing functions of Cisco Remote PHY Software could allow an unauthenticated, remote attacker to impact traffic passing through a device, potentially causing a denial of service (DoS) condition. The vulnerability is due to the affected software not validating and calculating certain numerical values in IPv4 packets that are sent to an affected device. An attacker could exploit this vulnerability by sending malformed IPv4 traffic to an affected device. A successful exploit could allow the attacker to disrupt the flow of certain IPv4 traffic passing through an affected device, which could result in a 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

This vulnerability exists in IPv4 fragment-processing functions of Cisco Remote PHY Software. The software fails to properly validate and calculate certain numerical values in IPv4 packets, allowing malformed IPv4 traffic to cause a denial of service by disrupting the flow of IPv4 traffic passing through the affected device.

MitigationApply the Cisco-provided patch or software update for Remote PHY Software to address the IPv4 fragment validation flaw. Until patched, consider implementing network-level filtering of malformed IPv4 fragments as a temporary mitigation.

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
RemoteApplication
Affected:= phy

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. Confirm Cisco Remote PHY Software is installed
    Identify the device and software running on it. Check the system for Cisco Remote PHY Software components or review device inventory/documentation to confirm this specific product line is in use.
    Affected if The device or system is running Cisco Remote PHY Software as the operating environment.
  2. Determine if IPv4 forwarding/processing is enabled
    Review the device configuration to verify whether IPv4 packet forwarding or routing functionality is enabled. This is typically shown in network interface settings or routing configuration.
    Affected if IPv4 forwarding or processing is actively enabled on the device.
  3. Check if the device processes external IPv4 traffic
    Examine network traffic flows or interface statistics to determine whether the device is actively passing IPv4 packets from external sources through its processing functions.
    Affected if The device serves as a pass-through for IPv4 traffic from other network segments.
  4. Review software version against available patches
    Locate the installed software version string for Cisco Remote PHY Software through CLI, system UI, or firmware information. Compare this version to Cisco's official patch releases for CVE-2018-15391.
    Affected if The installed version matches or precedes the patched releases provided by Cisco for this CVE.

A system is affected if it runs Cisco Remote PHY Software with IPv4 forwarding enabled while processing or passing through IPv4 traffic, and the installed version predates the Cisco-provided patch for this vulnerability.

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 Cisco-provided patch or software update for Remote PHY Software to address the IPv4 fragment validation flaw. Until patched, consider implementing network-level filtering of malformed IPv4 fragments as a temporary mitigation.

Fix this in Remote Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2018-15391 — 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-2018-15391 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