Four vulnerabilities in the widely adopted ‘Stacked VLAN’ Ethernet feature allows attackers to perform denial-of-service (DoS) or man-in-the-middle (MitM) attacks against network targets using custom-crafted packets.
Stacked VLANs, also known as VLAN Stacking, is a feature in modern routers and switches that allows companies to encapsulate multiple VLAN IDs into a single VLAN connection shared with an upstream provider.
“With stacked VLANs, service providers can use a unique VLAN (called a service-provider VLAN ID, or SP-VLAN ID) to support customers who have multiple VLANs. Customer VLAN IDs (CE-VLAN IDs) are preserved and traffic from different customers is segregated within the service-provider infrastructure even when they appear to be on the same VLAN,” explains Cisco’s documentation on the feature.
The CERT Coordination Center disclosed the flaws yesterday after giving device vendors time to investigate, respond, and release security updates.
The vulnerabilities affect networking devices such as switches, routers, and operating systems that use Layer-2 (L2) security controls to filter traffic for virtual network isolation.
Cisco and Juniper Networks have confirmed that some of their products are impacted by the flaws, but numerous device vendors haven’t concluded their investigation; hence the overall impact remains unknown.
