CVE-2021-27853

MediumCVSS 4.7/10Last modified Jun 17, 2026

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.

Metrics

CVSS 3.1 4.7/10CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Weakness enumeration

CWE-290

Affected software

Vendor	Product	Versions
IEEE	802.2	>= 802.2h-1997, <= 802.2h-1997
IETF	draft-ietf-v6ops-ra-guard	>= 08, <= 08
IETF	P802.1Q	>= D1.0, <= D1.0

References

https://blog.champtar.fr/VLAN0_LLC_SNAP/Exploit, Third Party Advisory
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/Technical Description, Third Party Advisory
https://kb.cert.org/vuls/id/855201Third Party Advisory, US Government Resource
https://standards.ieee.org/ieee/802.1Q/10323/Vendor Advisory
https://standards.ieee.org/ieee/802.2/1048/Vendor Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTXThird Party Advisory
https://blog.champtar.fr/VLAN0_LLC_SNAP/Exploit, Third Party Advisory
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/Technical Description, Third Party Advisory
https://kb.cert.org/vuls/id/855201Third Party Advisory, US Government Resource
https://standards.ieee.org/ieee/802.1Q/10323/Vendor Advisory
https://standards.ieee.org/ieee/802.2/1048/Vendor Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTXThird Party Advisory
https://www.kb.cert.org/vuls/id/855201

Timeline

Published: Sep 27, 2022
Last modified: Jun 17, 2026
NVD status: Modified

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