Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer

{
  "id": "7f8153db358c0005df219a126f8defa6188683c1af8b9da494f6545991915ba6",
  "url": "https://osv.dev/vulnerability/CVE-2026-73299",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer",
    "summary": "Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, the TypeScript Nunjucks renderer evaluated untrusted .prompty template bodies with unrestricted JavaScript member access. An attacker-controlled template could traverse constructor and prototype properties to execute JavaScript in the host Node.js process. This issue is fixed in versions 0.1.5 and 2.0.0-beta.5.",
    "evidence": "osv:CVE-2026-73299",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-73299",
      "aliases": [
        "CVE-2026-73299",
        "GHSA-w28w-gp39-m4p6"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/microsoft/prompty",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "8ea0e74222e1e35b51232878b1ae32adecf1ac14"
                },
                {
                  "introduced": "30acb714bf68259760916c97b0c8fdaf1c5a75a0"
                },
                {
                  "fixed": "d8891f66b93bfa37f0611186258c953e12e87fd3"
                },
                {
                  "fixed": "e4a0ebf49e3a78d5d7796c8480bf9a4f0c54d19e"
                },
                {
                  "fixed": "f5c57c94a0990cca79d095c3daab661b4b1fb89f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.1.5"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "2.0.0-alpha.1"
                      },
                      {
                        "fixed": "2.0.0-beta.5"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e4a0ebf49e3a78d5d7796c8480bf9a4f0c54d19e"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f5c57c94a0990cca79d095c3daab661b4b1fb89f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "csharp/2.0.0-beta.3",
            "rust/2.0.0-beta.3",
            "typescript/2.0.0-beta.4",
            "python/2.0.0b3",
            "typescript/2.0.0-beta.3",
            "python/2.0.0b2",
            "typescript/2.0.0-beta.2",
            "rust/2.0.0-beta.2",
            "csharp/2.0.0-beta.2",
            "python/2.0.0b1",
            "typescript/2.0.0-beta.1",
            "rust/2.0.0-beta.1",
            "csharp/2.0.0-beta.1",
            "rust/2.0.0-alpha.12",
            "typescript/2.0.0-alpha.11",
            "rust/2.0.0-alpha.11",
            "python/2.0.0a11",
            "csharp/2.0.0-alpha.11",
            "csharp/2.0.0-alpha.10",
            "rust/2.0.0-alpha.10",
            "typescript/2.0.0-alpha.10",
            "python/2.0.0a10",
            "rust/2.0.0-alpha.9",
            "typescript/2.0.0-alpha.9",
            "python/2.0.0a9",
            "csharp/2.0.0-alpha.9",
            "rust/2.0.0-alpha.8",
            "typescript/2.0.0-alpha.8",
            "python/2.0.0a8",
            "csharp/2.0.0-alpha.8",
            "typescript/2.0.0-alpha.7",
            "csharp/2.0.0-alpha.7",
            "python/2.0.0a7",
            "csharp/2.0.0-alpha.6",
            "typescript/2.0.0-alpha.6",
            "python/2.0.0a6",
            "csharp/2.0.0-alpha.2",
            "csharp/2.0.0-alpha.1",
            "python/0.1.4",
            "python/0.1.3",
            "python/0.1.2",
            "python/0.1.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-73299.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.120014686Z",
      "provider": "osv",
      "references": [
        "https://github.com/microsoft/prompty/tree/typescript/2.0.0-beta.5",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73299.json",
        "https://github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39-m4p6",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-73299",
        "https://github.com/microsoft/prompty/commit/e4a0ebf49e3a78d5d7796c8480bf9a4f0c54d19e",
        "https://github.com/microsoft/prompty/commit/f5c57c94a0990cca79d095c3daab661b4b1fb89f",
        "https://github.com/microsoft/prompty/pull/404",
        "https://github.com/microsoft/prompty/pull/405"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1336",
          "CWE-94"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73299.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-73299",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517601,
  "published_at": "2026-08-12T17:31:38.807+00:00"
}