dbcve.org
Wireless Lan Controller SoftwareOperating system · Cisco

CVE-2018-0252

HIGH · 8.6 CVSS v3.0 Published 2018-05-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
Remediation priority · Urgent
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 IP Version 4 (IPv4) fragment reassembly function of Cisco 3500, 5500, and 8500 Series Wireless LAN Controller Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to a corruption of an internal data structure process that occurs when the affected software reassembles certain IPv4 packets. An attacker could exploit this vulnerability by sending certain malformed IPv4 fragments to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. This vulnerability affects all releases of 8.4 until the first fixed release for the 5500 and 8500 Series Wireless LAN Controllers and releases 8.5.103.0 and 8.5.105.0 for the 3500, 5500, and 8500 Series Wireless LAN Controllers. Cisco Bug IDs: CSCvf89222.

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 is a denial of service vulnerability in Cisco Wireless LAN Controllers (3500, 5500, 8500 series) where malformed IPv4 fragments trigger corruption of an internal data structure during the fragment reassembly process, causing the affected device to unexpectedly reload.

MitigationApply the Cisco firmware update that addresses this vulnerability. Until patched, consider implementing network-based filtering of suspicious IPv4 fragment traffic to reduce exploitability.

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
Wireless Lan Controller SoftwareOperating system
Affected:= 8.4\(100.0\)= 8.5\(107.30\)= 8.5\(107.41\)= 8.6\(1.108\)

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
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/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 WLC model
    Log into the controller CLI and run 'show inventory' or check the physical device label to confirm it is a 3500, 5500, or 8500 series Wireless LAN Controller
    Affected if The device is not one of these three model series
  2. Check the installed software version
    Log into the controller CLI and run 'show version' to display the software version number
    Affected if The displayed version is exactly 8.4(100.0), 8.5(107.30), 8.5(107.41), or 8.6(1.108)
  3. Verify IPv4 fragment processing is enabled
    Run 'show running-config | include ip fragment' or check the controller configuration for IPv4 fragment reassembly settings
    Affected if IPv4 fragment reassembly processing is enabled on the controller
  4. Review system logs for unexpected reloads
    Run 'show logs' or 'show reload history' to check for recent system reloads and look for messages related to IPv4 fragment handling or data structure corruption
    Affected if The device has recently reloaded unexpectedly with fragment reassembly-related error messages in the logs

You are affected if you are running one of the four specific vulnerable versions (8.4(100.0), 8.5(107.30), 8.5(107.41), or 8.6(1.108)) on a 3500, 5500, or 8500 series WLC with IPv4 fragment processing enabled.

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 firmware update that addresses this vulnerability. Until patched, consider implementing network-based filtering of suspicious IPv4 fragment traffic to reduce exploitability.

Fix this in Wireless Lan Controller Software 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-2018-0252 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