CVE-2021-27854
MEDIUMIEEE 802.2 < 802.2h-1997 - Authentication Bypass via VLAN 0 and LLC/SNAP Header Spoofing
Title source: llmDescription
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using combinations of VLAN 0 headers, LLC/SNAP headers, and converting frames from Ethernet to Wifi and its reverse.
References (6)
Core 6
Core References
Various Sources
https://blog.champtar.fr/VLAN0_LLC_SNAP/
Vendor Advisory
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
Vendor Advisory
https://standards.ieee.org/ieee/802.1Q/10323/
Vendor Advisory
https://standards.ieee.org/ieee/802.2/1048/
Third Party Advisory, US Government Resource
https://kb.cert.org/vuls/id/855201
Third Party Advisory, US Government Resource
https://www.kb.cert.org/vuls/id/855201
Scores
CVSS v3
4.7
EPSS
0.0066
EPSS Percentile
46.5%
Attack Vector
ADJACENT_NETWORK
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-290
Status
published
Products (2)
ieee/ieee_802.2
< 802.2h-1997
ietf/p802.1q
< d1.0
Published
Sep 27, 2022
Tracked Since
Feb 18, 2026