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Ios XeOperating system · Cisco

CVE-2020-3492

HIGH · 8.6 CVSS v3.1 Published 2020-09-24
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 Flexible NetFlow Version 9 packet processor of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers and Cisco AireOS Software for Cisco Wireless LAN Controllers (WLC) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient validation of certain parameters in a Flexible NetFlow Version 9 record. An attacker could exploit this vulnerability by spoofing the address of an existing Access Point on the network and sending a Control and Provisioning of Wireless Access Points (CAPWAP) packet that includes a crafted Flexible NetFlow Version 9 record to an affected device. A successful exploit could allow the attacker to cause a process crash that would lead to a reload of the device.

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 the Flexible NetFlow Version 9 packet processor of Cisco IOS XE and AireOS Wireless Controllers allows unauthenticated remote attackers to cause denial of service. The flaw stems from insufficient validation of certain parameters in a crafted Flexible NetFlow Version 9 record within CAPWAP packets. Attackers spoof an existing Access Point's address and send a malicious CAPWAP packet containing a malformed NetFlow record, triggering a process crash that forces device reload.

MitigationApply the Cisco security updates for CVE-2020-3492 to affected Catalyst 9800 Series Wireless Controllers and Wireless LAN Controllers. As a compensating control, consider restricting CAPWAP traffic to trusted sources or disabling Flexible NetFlow if not required, though patching is the primary remediation.

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:= 16.12.1

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
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/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 device type and IOS XE version
    Run 'show version' or 'show inventory' to confirm the device is a Cisco IOS XE or AireOS Wireless Controller and note the exact software version.
    Affected if Device is running Cisco IOS XE version 16.12.1
  2. Verify Flexible NetFlow is enabled
    Run 'show flow monitor' to list configured flow monitors, or check the running configuration for 'flow monitor' or 'flexible netflow' statements.
    Affected if Flexible NetFlow is configured and active on the device
  3. Confirm CAPWAP is in use
    Run 'show capwap summary' or check running config for 'capwap' related commands to verify the device is accepting CAPWAP connections from wireless access points.
    Affected if CAPWAP is enabled and the device functions as a wireless controller or supports CAPWAP
  4. Check for flow monitor bindings to interfaces
    Run 'show flow interface' to see which interfaces have flow monitors applied, particularly on wireless-related or management interfaces.
    Affected if Flow monitors are bound to active interfaces processing CAPWAP traffic
  5. Review NetFlow record configuration
    Run 'show flow exporter' and 'show flow record' to examine the configured NetFlow Version 9 records and templates.
    Affected if Flexible NetFlow Version 9 records are configured

The device is affected if it runs IOS XE version 16.12.1, has Flexible NetFlow enabled, and processes CAPWAP traffic, as the vulnerability is triggered by malformed NetFlow Version 9 records within CAPWAP packets.

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 security updates for CVE-2020-3492 to affected Catalyst 9800 Series Wireless Controllers and Wireless LAN Controllers. As a compensating control, consider restricting CAPWAP traffic to trusted sources or disabling Flexible NetFlow if not required, though patching is the primary remediation.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2020-3492 in production — separate from our analysis above.

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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
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  • Version or environment caveats, and links to real fixes
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