{"id":"CVE-2021-27853","state":"PUBLISHED","title":"L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers","description":"Layer 2 network filtering capabilities such as IPv6 RA guard or ARP inspection can be bypassed using combinations of VLAN 0 headers and LLC/SNAP headers.","publishedAt":"2022-09-27T17:55:09.203Z","updatedAt":"2025-11-04T19:12:25.432Z","severity":{"score":4.7,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","source":"CISA-ADP"},"assigner":"certcc","products":["IEEE 802.2","IETF draft-ietf-v6ops-ra-guard","IETF 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