FKIE_CVE-2021-27861

Vulnerability from fkie_nvd - Published: 2022-09-27 19:15 - Updated: 2026-06-17 03:45
Severity
4.7 (Medium) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
4.7 (Medium) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Summary
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
References
cret@cert.orghttps://blog.champtar.fr/VLAN0_LLC_SNAP/
cret@cert.orghttps://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/Third Party Advisory
cret@cert.orghttps://kb.cert.org/vuls/id/855201
cret@cert.orghttps://standards.ieee.org/ieee/802.1Q/10323/Third Party Advisory
cret@cert.orghttps://standards.ieee.org/ieee/802.2/1048/Third Party Advisory
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/Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://kb.cert.org/vuls/id/855201
af854a3a-2127-422b-91ae-364da2661108https://standards.ieee.org/ieee/802.1Q/10323/Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://standards.ieee.org/ieee/802.2/1048/Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://www.kb.cert.org/vuls/id/855201
Impacted products
Vendor Product Version
ieee ieee_802.2 *
ietf p802.1q *
To clipboard 

{
  "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"
    }
  ]
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.