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Vulnerability record · CVE-2021-27853 · published 27 September 2022

CVE-2021-27853: Ieee 802.2 authentication bypass by spoofing vulnerability

Ieee · Ieee 802.2

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.

4.7 CVSS 3.1 Medium EPSS 0.81% · top 44.2% CWE-290 · Authentication bypass by spoofing
4.7CVSS 3.1 base score
0.81%EPSS exploitation probability, 30 days
NoNot in CISA KEV
96Affected product versions listed by NVD
13References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

96 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://blog.champtar.fr/VLAN0_LLC_SNAP/ ExploitThird Party Advisory
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/ Technical DescriptionThird Party Advisory
https://kb.cert.org/vuls/id/855201 Third Party AdvisoryUS 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-J3z8CKTX Third Party Advisory
https://blog.champtar.fr/VLAN0_LLC_SNAP/ ExploitThird Party Advisory
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/ Technical DescriptionThird Party Advisory
https://kb.cert.org/vuls/id/855201 Third Party AdvisoryUS 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-J3z8CKTX Third Party Advisory
https://www.kb.cert.org/vuls/id/855201

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-27853), CISA KEV, FIRST EPSS (scores of 2026-10-10). This page is refreshed as NVD updates the record.