Microsoft Security Advisory CVE-2026-96222 - .NET Spoofing Vulnerability

{
  "id": "1816e647c35e3b7a7435a04859fa08917c00616f546e5afa87a81d1cb78b9bcb",
  "url": "https://osv.dev/vulnerability/GHSA-vrv5-2jg9-4mmr",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Microsoft Security Advisory CVE-2026-96222 - .NET Spoofing Vulnerability",
    "summary": "## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in System.Security.Cryptography.Xml. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. `KeyInfoX509Data` can accept serialized certificate formats containing attacker-controlled chain metadata instead of requiring a plain X.509 certificate, contributing to certificate-forgery and token-spoofing paths. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/474 ## CVSS Details - **Version:** 3.1 - **Severity:** High - **Score:** 7.4 - **Vector:** `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N` - **Weakness:** CWE-295 (Improper Certificate Validation) ## Affected Platforms - **Platforms:** Windows, Linux, macOS - **Architectures:** All ## Affected Packages The vulnerability affects Microsoft .NET projects that use an affected package version listed below. Package name | Affected version | Patched version ------------ | ---------------- | --------------- [System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 8.0.0, <= 8.0.4 | 8.0.5 ## Advisory FAQ ### How do I know if I am affected? If using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability. ### How do I fix the issue? 1. To fix the issue please install the latest version of .NET. If you have installed o",
    "evidence": "osv:GHSA-vrv5-2jg9-4mmr",
    "products": [
      {
        "name": {
          "value": "System.Security.Cryptography.Xml",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "8.0.5",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "8.0.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "8.0.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "8.0.2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "8.0.3",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "8.0.4",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "GHSA-vrv5-2jg9-4mmr",
      "aliases": [
        "BIT-dotnet-2026-96222",
        "BIT-dotnet-sdk-2026-96222",
        "CVE-2026-96222",
        "GHSA-vrv5-2jg9-4mmr"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "8.0.0"
                },
                {
                  "fixed": "8.0.5"
                }
              ]
            }
          ],
          "package": {
            "name": "System.Security.Cryptography.Xml",
            "purl": "pkg:nuget/System.Security.Cryptography.Xml",
            "ecosystem": "NuGet"
          },
          "versions": [
            "8.0.0",
            "8.0.1",
            "8.0.2",
            "8.0.3",
            "8.0.4"
          ],
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-vrv5-2jg9-4mmr/GHSA-vrv5-2jg9-4mmr.json",
            "last_known_affected_version_range": "<= 8.0.4"
          }
        }
      ],
      "modified": "2026-10-21T12:11:16.647574999Z",
      "provider": "osv",
      "references": [
        "https://github.com/dotnet/runtime/security/advisories/GHSA-vrv5-2jg9-4mmr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-96222",
        "https://github.com/dotnet/announcements/issues/474",
        "https://github.com/dotnet/runtime/issues/135705",
        "https://github.com/dotnet/runtime",
        "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-96222"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295"
        ],
        "severity": "HIGH",
        "github_reviewed": true,
        "nvd_published_at": "2026-10-13T19:21:48Z",
        "github_reviewed_at": "2026-10-13T20:45:13Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-96222",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 393028,
  "published_at": "2026-10-13T20:45:13+00:00"
}