CVE-2021-27862

MEDIUMNVD 4.74.7—

4.7

Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length and Ethernet to Wifi frame conversion (and optionally VLAN0 headers).

CVSS v3: 4.7
EG Score: 4.7(medium)
EPSS: 24.9%
KEV: Not listed

Published

September 27, 2022

Last Modified

November 4, 2025

References (9)

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/802.2/1048/
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/802.2/1048/
af854a3a-2127-422b-91ae-364da2661108https://www.kb.cert.org/vuls/id/855201

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 7× 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.

2026-05-27 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-2021-27862?

CVE-2021-27862 is a medium vulnerability published on September 27, 2022. Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length and Ethernet to Wifi frame conversion (and optionally VLAN0 headers).

When was CVE-2021-27862 disclosed?

CVE-2021-27862 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-2021-27862 actively exploited?

CVE-2021-27862 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 24.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-27862?

CVE-2021-27862 has a CVSS v3 base score of 4.7 (NVD).

How do I remediate CVE-2021-27862?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-27862, 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-2021-27862

📅 Published

🔄 Last Modified

🔗 References (9)