dbcve.org
Ios XeOperating system · Cisco

CVE-2021-34770

CRITICAL · 9.8 CVSS v3.1 Published 2021-09-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
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 Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, remote attacker to execute arbitrary code with administrative privileges or cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a logic error that occurs during the validation of CAPWAP packets. An attacker could exploit this vulnerability by sending a crafted CAPWAP packet to an affected device. A successful exploit could allow the attacker to execute arbitrary code with administrative privileges or 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

This is a critical vulnerability in the CAPWAP (Control and Provisioning of Wireless Access Points) protocol implementation within Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers. The flaw is a logic error during CAPWAP packet validation that allows an unauthenticated remote attacker to send specially crafted CAPWAP packets and either execute arbitrary code with administrative/root privileges or crash the device, causing denial of service.

MitigationApply the Cisco software update (CSCvw32322) that addresses this vulnerability. If immediate patching is not possible, consider network segmentation to limit exposure of affected wireless controllers to untrusted networks and monitor for anomalous CAPWAP traffic.

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:all versions= 3.15.1xbs= 3.15.2xbs= 16.6.4s= 16.10.1= 16.10.1e= 16.10.1s= 16.11.1= 16.11.1a= 16.11.1b= 16.11.1c= 16.11.2

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 model and software platform
    Use 'show version' or 'show inventory' command to confirm the device is a Cisco Catalyst 9000 Family Wireless Controller running Cisco IOS XE software
    Affected if Device is not a Catalyst 9000 Family Wireless Controller or does not run IOS XE
  2. Determine IOS XE version
    Execute 'show version' and locate the IOS XE version string (e.g., 16.10.1, 16.11.1)
    Affected if The installed IOS XE version matches one of the listed affected versions (3.15.1xbs, 3.15.2xbs, 16.6.4s, 16.10.1, 16.10.1e, 16.10.1s, 16.11.1, 16.11.1a, 16.11.1b, 16.11.1c, 16.11.2) or falls within version ranges containing these releases
  3. Verify CAPWAP protocol is enabled
    Check if the wireless controller has CAPWAP functionality active using 'show capwap status' or by confirming the device is functioning as a wireless controller with associated APs via 'show ap summary'
    Affected if CAPWAP protocol is enabled and the device accepts CAPWAP connections from access points (default state for a functioning wireless controller)
  4. Assess network exposure
    Review interface configurations and ACLs to determine if the CAPWAP UDP ports (5246/5247) are exposed to untrusted or external networks
    Affected if CAPWAP management interface is reachable from untrusted networks or the internet

The environment is affected if the device is a Cisco Catalyst 9000 Wireless Controller running a vulnerable IOS XE version and CAPWAP is active, especially if 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 Cisco software update (CSCvw32322) that addresses this vulnerability. If immediate patching is not possible, consider network segmentation to limit exposure of affected wireless controllers to untrusted networks and monitor for anomalous CAPWAP traffic.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,840
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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-2021-34770 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
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