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CVE-2018-8340

Status: ModifiedMedium (6.5)—

A security feature bypass vulnerability exists when Active Directory Federation Services (AD FS) improperly handles multi-factor authentication requests, aka "AD FS Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows Server 2012 R2, Windows 10 Servers.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (2)

Microsoft — Windows Server 2012Microsoft — Windows Server 2016

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2018-8340",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:S/C:P/I:N/A:N",
          "authentication": "SINGLE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV30": [
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        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 6.5,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "secure@microsoft.com",
      "affectedData": [
        {
          "vendor": "Microsoft",
          "product": "Windows Server 2016",
          "versions": [
            {
              "status": "affected",
              "version": "(Server Core installation)"
            }
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Windows Server 2012 R2",
          "versions": [
            {
              "status": "affected",
              "version": "(Server Core installation)"
            }
          ]
        },
        {
          "vendor": "Microsoft",
          "product": "Windows 10 Servers",
          "versions": [
            {
              "status": "affected",
              "version": "version 1709  (Server Core Installation)"
            },
            {
              "status": "affected",
              "version": "version 1803  (Server Core Installation)"
            }
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        }
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    }
  ],
  "published": "2018-08-15T17:29:03.907",
  "references": [
    {
      "url": "http://www.securityfocus.com/bid/105029",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "secure@microsoft.com"
    },
    {
      "url": "http://www.securitytracker.com/id/1041474",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "secure@microsoft.com"
    },
    {
      "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8340",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "secure@microsoft.com"
    },
    {
      "url": "http://www.securityfocus.com/bid/105029",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.securitytracker.com/id/1041474",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8340",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A security feature bypass vulnerability exists when Active Directory Federation Services (AD FS) improperly handles multi-factor authentication requests, aka \"AD FS Security Feature Bypass Vulnerability.\" This affects Windows Server 2016, Windows Server 2012 R2, Windows 10 Servers."
    },
    {
      "lang": "es",
      "value": "Existe una vulnerabilidad de omisión de característica de seguridad cuando ADFS (Active Directory Federation Services) gestiona incorrectamente peticiones de autenticación de múltiples factores. Esto también se conoce como \"ADFS Security Feature Bypass Vulnerability\". Esto afecta a Windows Server 2016, Windows Server 2012 R2 y Windows 10 Servers."
    }
  ],
  "lastModified": "2026-06-17T02:04:39.677",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "criteria": "cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*",
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              "matchCriteriaId": "DB18C4CE-5917-401E-ACF7-2747084FD36E"
            },
            {
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              "vulnerable": true,
              "matchCriteriaId": "041FF8BA-0B12-4A1F-B4BF-9C4F33B7C1E7"
            },
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            },
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              "vulnerable": true,
              "matchCriteriaId": "CAACE735-003E-4ACB-A82E-C0CF97D7F013"
            }
          ],
          "operator": "OR"
        }
      ]
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  ],
  "sourceIdentifier": "secure@microsoft.com"
}