dbcve.org
Aironet Access Point SoftwareOperating system · Cisco

CVE-2021-34740

HIGH · 7.4 CVSS v3.1 Published 2021-09-23
Fix available
A fix is available. Upgrade to 8.10.162.0 or later.
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
A vulnerability in the WLAN Control Protocol (WCP) implementation for Cisco Aironet Access Point (AP) software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to incorrect error handling when an affected device receives an unexpected 802.11 frame. An attacker could exploit this vulnerability by sending certain 802.11 frames over the wireless network to an interface on an affected AP. A successful exploit could allow the attacker to cause a packet buffer leak. This could eventually result in buffer allocation failures, which would trigger a reload of 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 vulnerability exists in the WLAN Control Protocol (WCP) implementation of Cisco Aironet Access Point software. The root cause is incorrect error handling when the AP receives an unexpected 802.11 frame. An unauthenticated, adjacent attacker within wireless range can exploit this by sending specially crafted 802.11 frames to the affected AP interface, causing a packet buffer leak. Over time, this leak leads to buffer allocation failures, triggering an automatic device reload and resulting in denial of service.

MitigationApply the Cisco software update for CVE-2021-34740 when available. As a temporary measure, monitor for unusual 802.11 frame patterns and device reloads on affected APs.

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
Aironet Access Point SoftwareOperating system
Affected:>= 8.10.0, < 8.10.162.0= 17.2= 17.3

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 Cisco Aironet AP model
    Run 'show version' on the AP CLI or check the AP model in the web interface. Confirm the device is a Cisco Aironet Access Point.
    Affected if The device is a Cisco Aironet Access Point model.
  2. Check installed software version
    Run 'show version' on the AP CLI and locate the 'IOS' or 'Software' version line. Compare this version number to the affected ranges.
    Affected if The installed version is >= 8.10.0 and < 8.10.162.0, OR equals exactly 17.2 or 17.3.
  3. Verify WCP protocol is active
    Run 'show controllers wlan' or 'show wcp' to confirm the WLAN Control Protocol is running. WCP is a built-in component of the AP software and cannot be disabled.
    Affected if The AP has an active wireless interface (radio enabled) - WCP processes 802.11 frames on any active AP interface.
  4. Check for unexpected device reloads
    Run 'show reload' or 'show crashinfo' to see reload history. Look for unexplained reloads or crash logs that may indicate buffer allocation failures.
    Affected if There are unexplained device reloads or crash logs showing buffer allocation failures.
  5. Review system logs for buffer errors
    Run 'show logging' or check syslog for messages containing 'buffer', 'allocation failed', or 'WCP' errors. These may appear before a reload event.
    Affected if Logs contain buffer allocation failures or WCP error messages.

A user is affected if they are running Cisco Aironet AP software version 8.10.0 through 8.10.161.x, 17.2, or 17.3 and the AP has an active radio interface, particularly if unexplained device reloads or buffer error messages are present.

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
Upgrade available Upgrade to 8.10.162.0 or later
Fixed in 8.10.162.0
Interim mitigation

Apply the Cisco software update for CVE-2021-34740 when available. As a temporary measure, monitor for unusual 802.11 frame patterns and device reloads on affected APs.

Recommended fix Moderate confidence

8.10.162.0 or later for 8.10.x branch; contact Cisco for specific fixed 17.x releases

  1. Identify the current running Cisco Aironet Access Point software version using 'show version' or the AP management interface
  2. For APs running Aironet software version 8.10.x: Upgrade to version 8.10.162.0 or later (8.10.162.0 is the first fixed release for this branch)
  3. For APs running version 17.2 or 17.3: Contact Cisco to obtain the specific fixed release for these branches, as the remediation path for 17.x versions requires vendor confirmation
  4. Schedule a maintenance window as the AP will need to be rebooted after the software upgrade
  5. Download the appropriate Cisco Aironet AP software from Cisco's software download center (tools.cisco.com)
  6. Upload the new firmware to the AP or wireless LAN controller (WLC) managing the APs
  7. Initiate the upgrade process via the WLC or directly on the AP
  8. Verify the upgrade completed successfully and confirm the new version is running with 'show version'
Caveat Review Cisco release notes for 8.10.162.0 for any functionality changes or migration requirements before upgrading

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

Fix this in Aironet Access Point Software Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2021-34740 in production — separate from our analysis above.

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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