CVE-2021-27854

MEDIUMNVD 4.74.7—

4.7

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.

CVSS v3: 4.7
EG Score: 4.7(medium)
EPSS: 28.7%
KEV: Not listed

Published

September 27, 2022

Last Modified

November 4, 2025

References (11)

cret@certhttps://blog.champtar.fr/VLAN0_LLC_SNAP/
cret@certhttps://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
cret@certhttps://kb.cert.org/vuls/id/855201
cret@certhttps://standards.ieee.org/ieee/802.1Q/10323/
cret@certhttps://standards.ieee.org/ieee/802.2/1048/
af854a3a-2127-422b-91ae-364da2661108https://blog.champtar.fr/VLAN0_LLC_SNAP/
af854a3a-2127-422b-91ae-364da2661108https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
af854a3a-2127-422b-91ae-364da2661108https://kb.cert.org/vuls/id/855201
af854a3a-2127-422b-91ae-364da2661108https://standards.ieee.org/ieee/802.1Q/10323/
af854a3a-2127-422b-91ae-364da2661108https://standards.ieee.org/ieee/802.2/1048/
af854a3a-2127-422b-91ae-364da2661108https://www.kb.cert.org/vuls/id/855201

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-290Authentication Bypass by Spoofing

Data Freshness Timeline

(refreshed 11× in last 7d / 18× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-25 14:37 UTCEG score recompute
2026-05-25 14:37 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2021-27854?

CVE-2021-27854 is a medium vulnerability published on September 27, 2022. 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.

When was CVE-2021-27854 disclosed?

CVE-2021-27854 was first published in the National Vulnerability Database on September 27, 2022, with the most recent update on November 4, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-27854 actively exploited?

CVE-2021-27854 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 28.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-27854?

CVE-2021-27854 has a CVSS v3 base score of 4.7 (NVD).

How do I remediate CVE-2021-27854?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-27854, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2021-27854

📅 Published

🔄 Last Modified

🔗 References (11)

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-27854?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (11)

Frequently asked(5)

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