---
id: CVE-2021-34740
title: >-
  Cisco Aironet Access Points WLAN Control Protocol Packet Buffer Leak Denial of
  Service Vulnerability (CVE-2021-34740)
summary: >-
  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…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'
cvssSource: vendor
vendor: Cisco
product: Cisco Aironet Access Point Software
affected:
  - aironet_access_point_software
  - aironet_access_point_software_ios_xe_controller
published: '2021-09-22'
updated: '2021-09-22'
sourceUpdated: '2021-09-22T16:00:00+00:00'
source: CSAF
sourceUrl: >-
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-airo-wpa-pktleak-dos-uSTyGrL
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-airo-wpa-pktleak-dos-uSTyGrL
  - url: 'https://software.cisco.com'
tags:
  - csaf
  - vendor-advisory
  - cisco
epss: 0.0036
epssPercentile: 0.29856
ingestedAt: '2026-09-08T15:58:18.543Z'
---

## Overview

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.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

## Vendor advisories

- **cisco-sa-airo-wpa-pktleak-dos-uSTyGrL** · Cisco · affected: Cisco Aironet Access Point Software, Cisco Aironet Access Point Software (IOS XE Controller) · updated 2021-09-22 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-airo-wpa-pktleak-dos-uSTyGrL)

**Cisco Aironet Access Points WLAN Control Protocol Packet Buffer Leak Denial of Service Vulnerability**. Released 2021-09-22.

Affected:

- Cisco Aironet Access Point Software
- Cisco Aironet Access Point Software (IOS XE Controller)

## Remediation

Cisco has released software updates that address this vulnerability. https://software.cisco.com