Roslyn CodeLens MCP Server: Untrusted Roslyn Analyzer Execution via get_diagnostics Leads to Arbitrary Code Execution

{
  "id": "203f4b6e10be1011f9e23b47ae936bf85c21223a08dcac11a7e637bad560c993",
  "url": "https://osv.dev/vulnerability/CVE-2026-45555",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Roslyn CodeLens MCP Server: Untrusted Roslyn Analyzer Execution via get_diagnostics Leads to Arbitrary Code Execution",
    "summary": "Roslyn CodeLens MCP Server is a Roslyn-based MCP server providing semantic code intelligence for .NET codebases. From 0.0.9 to 1.17.0, the get_diagnostics MCP tool loads and executes all DiagnosticAnalyzer assemblies referenced by the target solution without any allowlist, signature check, or user confirmation; includeAnalyzers defaults to true, so no explicit opt-in is required. An attacker who can place a malicious .csproj referencing an attacker-controlled DLL in a location the victim opens with the MCP server will achieve arbitrary code execution in the server process with the server's OS privileges. This vulnerability is fixed in 1.17.0.",
    "evidence": "osv:CVE-2026-45555",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-45555",
      "aliases": [
        "CVE-2026-45555",
        "GHSA-552p-8f74-6x7q"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/marcelroozekrans/roslyn-codelens-mcp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "56b6300607dabae7b2cc03653909c0ea89c69058"
                },
                {
                  "fixed": "3ac5c0ca73a8228fc641da65e423f347dfeb9520"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.0.9"
                      },
                      {
                        "fixed": "1.17.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.17.0"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.16.0",
            "v1.13.0",
            "v1.15.0",
            "v1.14.0",
            "v1.12.0",
            "v1.11.0",
            "v1.10.0",
            "v1.9.0",
            "v1.8.0",
            "v1.7.0",
            "v1.6.0",
            "v1.5.0",
            "v1.4.0",
            "v1.3.0",
            "v1.2.1",
            "v1.2.0",
            "v1.1.7",
            "v1.1.6",
            "v1.1.5",
            "v1.1.4",
            "v1.1.3",
            "v1.1.2",
            "v1.1.1",
            "v1.1.0",
            "v1.0.15",
            "v1.0.14",
            "v1.0.13",
            "v1.0.12",
            "v1.0.11",
            "v1.0.10",
            "v1.0.9",
            "v1.0.8",
            "v1.0.7",
            "v1.0.6",
            "v1.0.5",
            "v1.0.4",
            "v1.0.3",
            "v1.0.2",
            "v1.0.1",
            "v1.0.0",
            "v0.0.15",
            "v0.0.14",
            "v0.0.13",
            "v0.0.12",
            "v0.0.11",
            "v0.0.10",
            "v0.0.9"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45555.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.528890772Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45555.json",
        "https://github.com/MarcelRoozekrans/roslyn-codelens-mcp/security/advisories/GHSA-552p-8f74-6x7q",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45555"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-94"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45555.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-45555",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521271,
  "published_at": "2026-05-29T12:54:59.678+00:00"
}