CVE-2021-1439: Cisco Aironet Access Point Software

High severity, CVSS 7.4. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability in the multicast DNS (mDNS) gateway feature of Cisco Aironet Series Access Points Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation of incoming mDNS traffic. An attacker could exploit this vulnerability by sending a crafted mDNS packet to an affected device through a wireless network that is configured in FlexConnect local switching mode or through a wired network on a configured mDNS VLAN. A successful exploit could allow the attacker to cause the access point (AP) to reboot, resulting in a DoS condition.

Affected products

• Cisco Aironet Access Point Software: affected versions not specified
• Cisco Catalyst 9800 Firmware: from 17.1, before 17.3.3 (fixed in 17.3.3)

Published 2021-03-24. Last modified 2026-06-17.