CVE-2021-27861

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"state": "PUBLISHED", "cveId": "CVE-2021-27861", "assignerOrgId": "37e5125f-f79b-445b-8fad-9564f167944b", "assignerShortName": "certcc", "datePublished": "2022-09-27T18:40:13.742Z", "dateUpdated": "2025-11-04T19:12:27.712Z", "dateReserved": "2021-03-01T00:00:00.000Z"}, "containers": {"cna": {"title": "L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths", "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 LLC/SNAP headers with invalid length (and optionally VLAN0 headers)"}], "affected": [{"vendor": "IEEE", "product": "802.2", "versions": [{"version": "802.2h-1997", "status": "affected", "lessThanOrEqual": "802.2h-1997", "versionType": "custom"}]}, {"vendor": "IETF", "product": "draft-ietf-v6ops-ra-guard", "versions": [{"version": "08", "status": "affected", "lessThanOrEqual": "08", "versionType": "custom"}]}, {"vendor": "IETF", "product": "P802.1Q", "versions": [{"version": "D1.0", "status": "affected", "lessThanOrEqual": "D1.0", "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-130 Improper Handling of Length Parameter", "cweId": "CWE-130"}]}, {"descriptions": [{"type": "CWE", "lang": "en", "description": "CWE-290: Authentication Bypass by Spoofing", "cweId": "CWE-290"}]}], "source": {"discovery": "EXTERNAL"}}, "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"]}, {"url": "https://www.kb.cert.org/vuls/id/855201"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-04T19:12:27.712Z"}}, {"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": "2025-05-21T15:06:05.203947Z", "id": "CVE-2021-27861", "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": "2025-05-21T15:06:11.048Z"}}]}}

{"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"]}, {"url": "https://www.kb.cert.org/vuls/id/855201"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-04T19:12:27.712Z"}}, {"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-2021-27861", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2025-05-21T15:06:05.203947Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-05-21T15:05:32.573Z"}}], "cna": {"title": "L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "value": "Etienne Champetier (@champtar) <champetier.etienne@gmail.com>"}], "affected": [{"vendor": "IEEE", "product": "802.2", "versions": [{"status": "affected", "version": "802.2h-1997", "versionType": "custom", "lessThanOrEqual": "802.2h-1997"}]}, {"vendor": "IETF", "product": "draft-ietf-v6ops-ra-guard", "versions": [{"status": "affected", "version": "08", "versionType": "custom", "lessThanOrEqual": "08"}]}, {"vendor": "IETF", "product": "P802.1Q", "versions": [{"status": "affected", "version": "D1.0", "versionType": "custom", "lessThanOrEqual": "D1.0"}]}], "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 LLC/SNAP headers with invalid length (and optionally VLAN0 headers)"}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-130", "description": "CWE-130 Improper Handling of Length Parameter"}]}, {"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-2021-27861", "state": "PUBLISHED", "dateUpdated": "2025-11-04T19:12:27.712Z", "dateReserved": "2021-03-01T00:00:00.000Z", "assignerOrgId": "37e5125f-f79b-445b-8fad-9564f167944b", "datePublished": "2022-09-27T18:40:13.742Z", "assignerShortName": "certcc"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"product": "802.2", "vendor": "IEEE", "versions": [{"lessThanOrEqual": "802.2h-1997", "status": "affected", "version": "802.2h-1997", "versionType": "custom"}]}, {"product": "draft-ietf-v6ops-ra-guard", "vendor": "IETF", "versions": [{"lessThanOrEqual": "08", "status": "affected", "version": "08", "versionType": "custom"}]}, {"product": "P802.1Q", "vendor": "IETF", "versions": [{"lessThanOrEqual": "D1.0", "status": "affected", "version": "D1.0", "versionType": "custom"}]}], "source": "cret@cert.org"}], "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 LLC/SNAP headers with invalid length (and optionally VLAN0 headers)"}, {"lang": "es", "value": "Las capacidades de filtrado de red de capa 2, como la protecci\u00f3n RA de IPv6, pueden omitirse usando encabezados LLC/SNAP con una longitud no v\u00e1lida (y, opcionalmente, encabezados VLAN0)"}], "id": "CVE-2021-27861", "lastModified": "2026-06-17T03:45:32.467", "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"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-27861", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2025-05-21T15:06:05.203947Z", "version": "2.0.3"}}]}, "published": "2022-09-27T19:15:09.330", "references": [{"source": "cret@cert.org", "url": "https://blog.champtar.fr/VLAN0_LLC_SNAP/"}, {"source": "cret@cert.org", "tags": ["Third Party 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": ["Third Party Advisory"], "url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"source": "cret@cert.org", "tags": ["Third Party 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": ["Third Party 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": ["Third Party Advisory"], "url": "https://standards.ieee.org/ieee/802.1Q/10323/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://standards.ieee.org/ieee/802.2/1048/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://www.kb.cert.org/vuls/id/855201"}], "sourceIdentifier": "cret@cert.org", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-130"}, {"lang": "en", "value": "CWE-290"}], "source": "cret@cert.org", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-290"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "Kernel: Layer 2 network filtering capabilities bypass with invalid length (and optionally VLAN0 headers)", "id": "2130301", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2130301"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "status": "draft"}, "details": ["Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)", "Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)"], "name": "CVE-2021-27861", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2022-09-27T10:30:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-27861\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-27861\nhttps://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-VU855201-J3z8CKTX.html"], "threat_severity": "Moderate"}

{}