MSRC_CVE-2026-21218

Vulnerability from csaf_microsoft - Published: 2026-02-10 00:00 - Updated: 2026-02-10 00:00
Summary
.NET Spoofing Vulnerability

Notes

Additional Resources
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle
Disclaimer
The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
Customer Action
Required. The vulnerability documented by this CVE requires customer action to resolve.

{
  "document": {
    "acknowledgments": [
      {
        "names": [
          "\u003ca href=\"https://github.com/vcsjones\"\u003evcsjones\u003c/a\u003e with GitHub"
        ]
      }
    ],
    "aggregate_severity": {
      "namespace": "https://www.microsoft.com/en-us/msrc/security-update-severity-rating-system",
      "text": "Important"
    },
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      },
      {
        "category": "general",
        "text": "Required. The vulnerability documented by this CVE requires customer action to resolve.",
        "title": "Customer Action"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-21218 .NET Spoofing Vulnerability - HTML",
        "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21218"
      },
      {
        "category": "self",
        "summary": "CVE-2026-21218 .NET Spoofing Vulnerability - CSAF",
        "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-21218.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Exploitability Index",
        "url": "https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": ".NET Spoofing Vulnerability",
    "tracking": {
      "current_release_date": "2026-02-10T00:00:00.000Z",
      "generator": {
        "date": "2026-02-13T20:11:29.915Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-21218",
      "initial_release_date": "2026-02-10T00:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-02-10T00:00:00.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Mac OS \u003c10.0.3",
              "product_id": "2"
            }
          },
          {
            "category": "product_version",
            "name": "10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Mac OS 10.0.3",
              "product_id": "20838"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 10.0 installed on Mac OS"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Windows \u003c10.0.3",
              "product_id": "3"
            }
          },
          {
            "category": "product_version",
            "name": "10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Windows 10.0.3",
              "product_id": "20837"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 10.0 installed on Windows"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Linux \u003c8.0.24",
              "product_id": "8"
            }
          },
          {
            "category": "product_version",
            "name": "8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Linux 8.0.24",
              "product_id": "12415"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 8.0 installed on Linux"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Windows \u003c8.0.24",
              "product_id": "9"
            }
          },
          {
            "category": "product_version",
            "name": "8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Windows 8.0.24",
              "product_id": "12414"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 8.0 installed on Windows"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Linux \u003c10.0.3",
              "product_id": "1"
            }
          },
          {
            "category": "product_version",
            "name": "10.0.3",
            "product": {
              "name": ".NET 10.0 installed on Linux 10.0.3",
              "product_id": "20839"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 10.0 installed on Linux"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Mac OS \u003c8.0.24",
              "product_id": "7"
            }
          },
          {
            "category": "product_version",
            "name": "8.0.24",
            "product": {
              "name": ".NET 8.0 installed on Mac OS 8.0.24",
              "product_id": "12416"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 8.0 installed on Mac OS"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Mac OS \u003c9.0.13",
              "product_id": "5"
            }
          },
          {
            "category": "product_version",
            "name": "9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Mac OS 9.0.13",
              "product_id": "12433"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 9.0 installed on Mac OS"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Linux \u003c9.0.13",
              "product_id": "6"
            }
          },
          {
            "category": "product_version",
            "name": "9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Linux 9.0.13",
              "product_id": "12432"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 9.0 installed on Linux"
      },
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Windows \u003c9.0.13",
              "product_id": "4"
            }
          },
          {
            "category": "product_version",
            "name": "9.0.13",
            "product": {
              "name": ".NET 9.0 installed on Windows 9.0.13",
              "product_id": "12434"
            }
          }
        ],
        "category": "product_name",
        "name": ".NET 9.0 installed on Windows"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-21218",
      "cwe": {
        "id": "CWE-166",
        "name": "Improper Handling of Missing Special Element"
      },
      "notes": [
        {
          "category": "general",
          "text": "Microsoft",
          "title": "Assigning CNA"
        },
        {
          "category": "faq",
          "text": "The score is based on no user account is needed to perform the attack.",
          "title": "According to the CVSS metric, the privileges required is none (PR:N). What does that mean for this vulnerability?"
        },
        {
          "category": "faq",
          "text": "An attacker who successfully exploited this vulnerability could bypass critical-header validation and the service may accept a message it should reject.",
          "title": "According to the CVSS metrics, successful exploitation of this vulnerability could lead to no loss of confidentiality (C:N) and availability (A:L), but could lead to major loss of integrity (I:H). What does that mean for this vulnerability?"
        }
      ],
      "product_status": {
        "fixed": [
          "12414",
          "12415",
          "12416",
          "12432",
          "12433",
          "12434",
          "20837",
          "20838",
          "20839"
        ],
        "known_affected": [
          "1",
          "2",
          "3",
          "4",
          "5",
          "6",
          "7",
          "8",
          "9"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-21218 .NET Spoofing Vulnerability - HTML",
          "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21218"
        },
        {
          "category": "self",
          "summary": "CVE-2026-21218 .NET Spoofing Vulnerability - CSAF",
          "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-21218.json"
        }
      ],
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-02-10T00:00:00.000Z",
          "details": "10.0.3:Security Update:https://support.microsoft.com/help/5077862",
          "product_ids": [
            "2",
            "3",
            "1"
          ],
          "url": "https://support.microsoft.com/help/5077862"
        },
        {
          "category": "vendor_fix",
          "date": "2026-02-10T00:00:00.000Z",
          "details": "8.0.24:Security Update:https://support.microsoft.com/help/5077863",
          "product_ids": [
            "8",
            "9",
            "7"
          ],
          "url": "https://support.microsoft.com/help/5077863"
        },
        {
          "category": "vendor_fix",
          "date": "2026-02-10T00:00:00.000Z",
          "details": "9.0.13:Security Update:https://support.microsoft.com/help/5077864",
          "product_ids": [
            "5",
            "6",
            "4"
          ],
          "url": "https://support.microsoft.com/help/5077864"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "environmentalsScore": 0.0,
            "exploitCodeMaturity": "UNPROVEN",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "remediationLevel": "OFFICIAL_FIX",
            "reportConfidence": "CONFIRMED",
            "scope": "UNCHANGED",
            "temporalScore": 6.5,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "products": [
            "1",
            "2",
            "3",
            "4",
            "5",
            "6",
            "7",
            "8",
            "9"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Spoofing"
        },
        {
          "category": "exploit_status",
          "details": "Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Unlikely"
        }
      ],
      "title": ".NET Spoofing Vulnerability"
    }
  ]
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Sightings

Author Source Type Date

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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Loading…

Detection rules are retrieved from Rulezet.

Loading…

Loading…