dbcve.org
Ios XeOperating system · Cisco

CVE-2021-34768

HIGH · 7.5 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 →
84/100
Remediation priority · High
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
Multiple vulnerabilities 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 cause a denial of service (DoS) condition on an affected device. These vulnerabilities are due to insufficient validation of CAPWAP packets. An attacker could exploit the 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.

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

Vulnerability in CAPWAP (Control and Provisioning of Wireless Access Points) protocol processing in Cisco IOS XE for Catalyst 9000 Family Wireless Controllers. Insufficient validation of incoming CAPWAP packets allows unauthenticated remote attackers to send malformed packets that cause the affected device to crash and reload, resulting in denial of service.

MitigationApply Cisco software updates/patches for IOS XE when released. Consider network segmentation to limit CAPWAP exposure and implement ingress filtering for CAPWAP traffic at network boundaries.

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:= 3.15.1xbs= 3.15.2xbs= 17.3.1= 17.3.2= 17.3.2a= 17.4.1= 17.5.1

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 and IOS XE version
    Execute 'show version' on the device CLI to display the running Cisco IOS XE version and confirm it is a Catalyst 9000 Family Wireless Controller
    Affected if The device is running Cisco IOS XE for Catalyst 9000 Family Wireless Controllers AND the version matches one of these: 3.15.1xbs, 3.15.2xbs, 17.3.1, 17.3.2, 17.3.2a, 17.4.1, or 17.5.1
  2. Confirm CAPWAP protocol is active
    Execute 'show wireless summary' or 'show capwap status' to verify the device has wireless controller functionality enabled and CAPWAP is running
    Affected if CAPWAP protocol is active and the device is a wireless controller (this condition is required for the vulnerability to be exploitable)

You are affected if your device is a Cisco Catalyst 9000 Series Wireless Controller running IOS XE version 3.15.1xbs, 3.15.2xbs, 17.3.1, 17.3.2, 17.3.2a, 17.4.1, or 17.5.1 with CAPWAP 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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco software updates/patches for IOS XE when released. Consider network segmentation to limit CAPWAP exposure and implement ingress filtering for CAPWAP traffic at network boundaries.

Recommended fix Moderate confidence

IOS XE 17.3.3 or later

  1. Identify the current IOS XE version running on the Cisco Catalyst 9000 Family Wireless Controller using 'show version' command
  2. Access the Cisco Software Download page or use the Cisco Bug Search Tool (tools.cisco.com) to find the fixed IOS XE release for this vulnerability
  3. Upgrade the device to IOS XE 17.3.3 or later (the next release after the affected 17.3.1 and 17.3.2 versions)
  4. Verify the upgrade was successful and the device is functioning properly
  5. Test CAPWAP functionality to ensure normal wireless controller operations
Caveat Standard upgrade risks apply - ensure compatibility with existing wireless configurations and review release notes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2021-34768 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