dbcve.org
Ios XeOperating system · Cisco

CVE-2021-34769

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

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

MitigationApply the Cisco IOS XE software update addressing CVE-2021-34769. Until patched, consider network segmentation or ACLs to limit CAPWAP packet sources to trusted WTP (Wireless Termination Points).

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 model and type
    Run 'show version' or 'show inventory' to confirm the device is a Catalyst 9000 Series Wireless Controller (e.g., C9800-CL, C9800-L, C9800-40, C9800-80)
    Affected if Device is not a Catalyst 9000 Family Wireless Controller - not affected
  2. Check IOS XE version
    Run 'show version' and locate the Cisco IOS XE software version (e.g., 17.5.1, 17.4.1, etc.)
    Affected if Version matches 3.15.1xbs, 3.15.2xbs, 17.3.1, 17.3.2, 17.3.2a, 17.4.1, or 17.5.1 - potentially affected
  3. Verify wireless/CAPWAP feature is active
    Run 'show wireless summary' or 'show capwap summary' to confirm the wireless controller is enabled and processing CAPWAP traffic
    Affected if Wireless controller is not enabled or CAPWAP is not active - not affected
  4. Check CAPWAP port exposure
    Review interface configurations and ACLs for UDP ports 5246 (CAPWAP control) and 5247 (CAPWAP data). Check if these ports are accessible from untrusted networks using 'show ip interface' and access-list inspections
    Affected if CAPWAP ports are exposed to untrusted or management networks - vulnerable to remote attack

Affected if the device is a Catalyst 9000 Wireless Controller running one of the listed IOS XE versions with CAPWAP enabled and exposed to untrusted network segments.

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 the Cisco IOS XE software update addressing CVE-2021-34769. Until patched, consider network segmentation or ACLs to limit CAPWAP packet sources to trusted WTP (Wireless Termination Points).

Recommended fix Moderate confidence

Upgrade to Cisco IOS XE 17.3.3 or later (or the next stable 17.x release indicated in the Cisco security advisory)

  1. 1. Identify the current Cisco IOS XE version on the affected Catalyst 9000 Family Wireless Controller using 'show version' command.
  2. 2. Back up the current device configuration using 'copy running-config startup-config' or export to a secure location.
  3. 3. Schedule a maintenance window as the upgrade will require a device reload.
  4. 4. Download the fixed Cisco IOS XE software release from Cisco's download portal (tools.cisco.com) - look for the security advisory associated with CVE-2021-34769.
  5. 5. Upload the new IOS XE image to the device using TFTP, FTP, or SCP.
  6. 6. Configure the new boot variable: 'boot system flash:<new_image_name>'.
  7. 7. Save configuration: 'write memory' or 'copy running-config startup-config'.
  8. 8. Reload the device: 'reload'.
Caveat Standard IOS XE upgrade risks apply - ensure configuration compatibility and test in lab environment before production deployment

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
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-34769 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