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Ios XeOperating system · Cisco

CVE-2020-3494

HIGH · 7.4 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 →
79/100
Remediation priority · High
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
Multiple vulnerabilities in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition of an affected device. These vulnerabilities are due to insufficient validation of CAPWAP packets. An attacker could exploit these vulnerabilities by sending a malformed CAPWAP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition on the affected 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

This CVE involves multiple vulnerabilities in the CAPWAP (Control and Provisioning of Wireless Access Points) protocol handler of Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers. The vulnerabilities stem from insufficient validation of incoming CAPWAP packets, allowing an unauthenticated attacker on the adjacent network segment to send malformed packets that trigger a device crash and reload, resulting in denial of service.

MitigationApply the appropriate Cisco IOS XE software update for the Catalyst 9800 Series Wireless Controllers. Implement network segmentation to restrict adjacent network access to CAPWAP interfaces, reducing the attack surface until patches can be deployed.

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 device model
    Run 'show version' or 'show inventory' to confirm the device is a Cisco Catalyst 9800 Series Wireless Controller
    Affected if The device is not a Catalyst 9800 Series Wireless Controller (not affected)
  2. Check the IOS XE software version
    Run 'show version' and locate the 'IOS XE' or 'Version' line. Confirm the exact version is 16.12.1
    Affected if The installed version is exactly 16.12.1 (affected)
  3. Verify CAPWAP protocol is enabled
    Run 'show capwap summary' or check the wireless controller configuration with 'show running-config | include capwap'
    Affected if CAPWAP is enabled (required for the vulnerability to be exploitable)
  4. Assess network accessibility to CAPWAP interfaces
    Check if CAPWAP UDP ports (5246, 5247) are accessible from adjacent network segments by reviewing interface configurations and ACLs
    Affected if CAPWAP interfaces are reachable from untrusted adjacent networks (exploitable condition)

A user is affected if they are running Cisco IOS XE version 16.12.1 on a Catalyst 9800 Series Wireless Controller with CAPWAP enabled and accessible from the adjacent network.

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 for the Catalyst 9800 Series Wireless Controllers. Implement network segmentation to restrict adjacent network access to CAPWAP interfaces, reducing the attack surface until patches can be deployed.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2020-3494 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