CVE-2021-27854 - Vulnerability Details - OpenCVE

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.

No CVSS v4.0

Attack Vector Adjacent Network

Attack Complexity Low

Privileges Required None

Scope Changed

Confidentiality Impact None

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00025.

Exploitation none

Automatable no

Technical Impact partial

Vendors	Products
Ieee	Ieee 802.2
Ietf	P802.1q

Configuration 1 [-]

cpe:2.3:a:ieee:ieee_802.2:*:*:*:*:*:*:*:*

Configuration 2 [-]

cpe:2.3:a:ietf:p802.1q:*:*:*:*:*:*:*:*

No data.

No data.

References

Link	Providers
https://blog.champtar.fr/VLAN0_LLC_SNAP/
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
https://kb.cert.org/vuls/id/855201
https://nvd.nist.gov/vuln/detail/CVE-2021-27854
https://standards.ieee.org/ieee/802.1Q/10323/
https://standards.ieee.org/ieee/802.2/1048/
https://www.cve.org/CVERecord?id=CVE-2021-27854

History

Wed, 21 May 2025 16:15:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

MITRE

Status: PUBLISHED

Assigner: certcc

Published: 2022-09-27T18:40:12.738Z

Updated: 2025-05-21T15:06:44.230Z

Reserved: 2021-03-01T00:00:00.000Z

Link: CVE-2021-27854

Vulnrichment

Updated: 2024-08-03T21:33:15.949Z

NVD

Status : Modified

Published: 2022-09-27T19:15:09.240

Modified: 2025-05-21T15:15:54.267

Link: CVE-2021-27854

Redhat

Severity : Moderate

Publid Date: 2021-09-27T10:30:00Z

Links: CVE-2021-27854 - Bugzilla

OpenCVE Enrichment

No data.

{"dataType": "CVE_RECORD", "dataVersion": "5.1", "cveMetadata": {"state": "PUBLISHED", "cveId": "CVE-2021-27854", "assignerOrgId": "37e5125f-f79b-445b-8fad-9564f167944b", "assignerShortName": "certcc", "datePublished": "2022-09-27T18:40:12.738Z", "dateUpdated": "2025-05-21T15:06:44.230Z", "dateReserved": "2021-03-01T00:00:00.000Z"}, "containers": {"cna": {"title": "L2 network filtering bypass using stacked VLAN0, LLC/SNAP headers, and Ethernet to Wifi frame translation", "datePublic": "2022-09-27T00:00:00.000Z", "providerMetadata": {"orgId": "37e5125f-f79b-445b-8fad-9564f167944b", "shortName": "certcc", "dateUpdated": "2022-10-12T00:00:00.000Z"}, "descriptions": [{"lang": "en", "value": "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."}], "affected": [{"vendor": "IETF", "product": "P802.1Q", "versions": [{"version": "D1.0", "status": "affected", "lessThanOrEqual": "D1.0", "versionType": "custom"}]}, {"vendor": "IETF", "product": "draft-ietf-v6ops-ra-guard", "versions": [{"version": "08", "status": "affected", "lessThanOrEqual": "08", "versionType": "custom"}]}, {"vendor": "IEEE", "product": "802.2", "versions": [{"version": "802.2h-1997", "status": "affected", "lessThanOrEqual": "802.2h-1997", "versionType": "custom"}]}], "references": [{"url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/"}, {"url": "https://standards.ieee.org/ieee/802.2/1048/"}, {"url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"url": "https://kb.cert.org/vuls/id/855201"}, {"url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/"}], "credits": [{"lang": "en", "value": "Etienne Champetier (@champtar) <champetier.etienne@gmail.com>"}], "problemTypes": [{"descriptions": [{"type": "CWE", "lang": "en", "description": "CWE-290: Authentication Bypass by Spoofing", "cweId": "CWE-290"}]}], "source": {"discovery": "EXTERNAL"}}, "adp": [{"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-03T21:33:15.949Z"}, "title": "CVE Program Container", "references": [{"url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/", "tags": ["x_transferred"]}, {"url": "https://standards.ieee.org/ieee/802.2/1048/", "tags": ["x_transferred"]}, {"url": "https://standards.ieee.org/ieee/802.1Q/10323/", "tags": ["x_transferred"]}, {"url": "https://kb.cert.org/vuls/id/855201", "tags": ["x_transferred"]}, {"url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/", "tags": ["x_transferred"]}]}, {"metrics": [{"cvssV3_1": {"scope": "CHANGED", "version": "3.1", "baseScore": 4.7, "attackVector": "ADJACENT_NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"timestamp": "2025-05-21T15:06:23.882465Z", "id": "CVE-2021-27854", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-05-21T15:06:44.230Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CVE Program Container", "references": [{"url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/", "tags": ["x_transferred"]}, {"url": "https://standards.ieee.org/ieee/802.2/1048/", "tags": ["x_transferred"]}, {"url": "https://standards.ieee.org/ieee/802.1Q/10323/", "tags": ["x_transferred"]}, {"url": "https://kb.cert.org/vuls/id/855201", "tags": ["x_transferred"]}, {"url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/", "tags": ["x_transferred"]}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-03T21:33:15.949Z"}}, {"title": "CISA ADP Vulnrichment", "metrics": [{"cvssV3_1": {"scope": "CHANGED", "version": "3.1", "baseScore": 4.7, "attackVector": "ADJACENT_NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2021-27854", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2025-05-21T15:06:23.882465Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-05-21T15:06:38.760Z"}}], "cna": {"title": "L2 network filtering bypass using stacked VLAN0, LLC/SNAP headers, and Ethernet to Wifi frame translation", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "value": "Etienne Champetier (@champtar) <champetier.etienne@gmail.com>"}], "affected": [{"vendor": "IETF", "product": "P802.1Q", "versions": [{"status": "affected", "version": "D1.0", "versionType": "custom", "lessThanOrEqual": "D1.0"}]}, {"vendor": "IETF", "product": "draft-ietf-v6ops-ra-guard", "versions": [{"status": "affected", "version": "08", "versionType": "custom", "lessThanOrEqual": "08"}]}, {"vendor": "IEEE", "product": "802.2", "versions": [{"status": "affected", "version": "802.2h-1997", "versionType": "custom", "lessThanOrEqual": "802.2h-1997"}]}], "datePublic": "2022-09-27T00:00:00.000Z", "references": [{"url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/"}, {"url": "https://standards.ieee.org/ieee/802.2/1048/"}, {"url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"url": "https://kb.cert.org/vuls/id/855201"}, {"url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/"}], "descriptions": [{"lang": "en", "value": "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."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-290", "description": "CWE-290: Authentication Bypass by Spoofing"}]}], "providerMetadata": {"orgId": "37e5125f-f79b-445b-8fad-9564f167944b", "shortName": "certcc", "dateUpdated": "2022-10-12T00:00:00.000Z"}}}, "cveMetadata": {"cveId": "CVE-2021-27854", "state": "PUBLISHED", "dateUpdated": "2025-05-21T15:06:44.230Z", "dateReserved": "2021-03-01T00:00:00.000Z", "assignerOrgId": "37e5125f-f79b-445b-8fad-9564f167944b", "datePublished": "2022-09-27T18:40:12.738Z", "assignerShortName": "certcc"}, "dataVersion": "5.1"}

{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ieee:ieee_802.2:*:*:*:*:*:*:*:*", "matchCriteriaId": "D5B0DDC2-21C5-4682-9AA2-055BF7C722DA", "versionEndIncluding": "802.2h-1997", "vulnerable": true}], "negate": false, "operator": "OR"}]}, {"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ietf:p802.1q:*:*:*:*:*:*:*:*", "matchCriteriaId": "94105D2E-950F-4290-8840-301FA908BC8C", "versionEndIncluding": "d1.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Las capacidades de filtrado de red de capa 2, como la protecci\u00f3n RA de IPv6, pueden omitirse usando combinaciones de encabezados VLAN 0, encabezados LLC/SNAP y convirtiendo tramas de Ethernet a Wifi y su inversa"}], "id": "CVE-2021-27854", "lastModified": "2025-05-21T15:15:54.267", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "NONE", "baseScore": 4.7, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "NONE", "baseScore": 4.7, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 1.4, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}, "published": "2022-09-27T19:15:09.240", "references": [{"source": "cret@cert.org", "url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/"}, {"source": "cret@cert.org", "tags": ["Vendor Advisory"], "url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/"}, {"source": "cret@cert.org", "url": "https://kb.cert.org/vuls/id/855201"}, {"source": "cret@cert.org", "tags": ["Vendor Advisory"], "url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"source": "cret@cert.org", "tags": ["Vendor Advisory"], "url": "https://standards.ieee.org/ieee/802.2/1048/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Vendor Advisory"], "url": "https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://kb.cert.org/vuls/id/855201"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Vendor Advisory"], "url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Vendor Advisory"], "url": "https://standards.ieee.org/ieee/802.2/1048/"}], "sourceIdentifier": "cret@cert.org", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-290"}], "source": "cret@cert.org", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-290"}], "source": "nvd@nist.gov", "type": "Primary"}]}