CVE-2005-4440: Vlan Protocol

Medium severity, CVSS 5.0. EPSS: 1.6% chance of exploitation in the next 30 days.

The 802.1q VLAN protocol allows remote attackers to bypass network segmentation and spoof VLAN traffic via a message with two 802.1q tags, which causes the second tag to be redirected from a downstream switch after the first tag has been stripped, as demonstrated by Yersinia, aka "double-tagging VLAN jumping attack."

Affected products

• Vlan Protocol Vlan Protocol: version 802.1q only

Published 2005-12-21. Last modified 2026-06-16.