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Ios XeOperating system · Cisco

CVE-2021-1373

HIGH · 8.6 CVSS v3.1 Published 2021-03-24
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 Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Wireless Controller Software for the Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition of an affected device. The vulnerability is due to insufficient validation of CAPWAP packets. An attacker could exploit this vulnerability 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.

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 CAPWAP protocol processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers allows an unauthenticated remote attacker to cause device crash and reload. The flaw is due to insufficient validation of CAPWAP packets, which can be exploited by sending malformed CAPWAP packets to the affected device.

MitigationApply the vendor-supplied security patch for Cisco IOS XE Wireless Controller Software. If patching is not immediately possible, consider network segmentation to limit exposure of the wireless controller to untrusted networks.

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:= 16.10.1= 16.10.1e= 16.10.1s= 16.11.1= 16.11.1a= 16.11.1b= 16.11.1c= 16.11.2= 16.12.1= 16.12.1s= 16.12.1t= 16.12.2s

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
    Run 'show version' or check the device model to confirm it is a Cisco Catalyst 9000 Family Wireless Controller (such as Catalyst 9800-CL, 9800-L, 9800-EL, or 9800 series)
    Affected if Device is not a Cisco Catalyst 9000 Family Wireless Controller - the vulnerability does not apply
  2. Check IOS XE version
    Run 'show version' and locate the 'IOS XE' or 'Version' line. Compare the full version number against the affected list: 16.10.1, 16.10.1e, 16.10.1s, 16.11.1, 16.11.1a, 16.11.1b, 16.11.1c, 16.11.2, 16.12.1, 16.12.1s, 16.12.1t, 16.12.2s
    Affected if Version exactly matches one of the listed versions - device is potentially affected
  3. Verify Wireless Controller feature is enabled
    Run 'show wireless summary' or 'show ap summary' to confirm the Wireless Controller functionality is active. CAPWAP is the protocol used for managing access points, so the wireless controller feature must be enabled for the vulnerability to be exploitable
    Affected if Wireless Controller feature is not enabled - the CAPWAP processing code path is not active and the device is not vulnerable to this specific flaw
  4. Assess network exposure
    Review the device management interface configuration using 'show running-config interface' for management interfaces. Determine if the wireless controller management or CAPWAP ports (UDP 5246, 5247) are accessible from untrusted networks
    Affected if Management interface or CAPWAP ports are exposed to untrusted networks - an attacker could send malformed CAPWAP packets to trigger the crash

The device is affected if it is a Cisco Catalyst 9000 Family Wireless Controller running IOS XE version 16.10.1 through 16.12.2s with the Wireless Controller feature enabled and with management or CAPWAP ports exposed to untrusted networks.

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 vendor-supplied security patch for Cisco IOS XE Wireless Controller Software. If patching is not immediately possible, consider network segmentation to limit exposure of the wireless controller to untrusted networks.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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Scan for this in your stack

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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-2021-1373 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