{
  "affected": [
    {
      "affectedData": [
        {
          "product": "fastify-reply-from",
          "vendor": "fastify",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.0.2"
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          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
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              "vulnerable": true
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          "negate": false,
          "operator": "OR"
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    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "fastify-reply-from is an npm package which is a fastify plugin to forward the current http request to another server. In fastify-reply-from before version 4.0.2, by crafting a specific URL, it is possible to escape the prefix of the proxied backend service. If the base url of the proxied server is \"/pub/\", a user expect that accessing \"/priv\" on the target service would not be possible. In affected versions, it is possible. This is fixed in version 4.0.2."
    },
    {
      "lang": "es",
      "value": "fastify-reply-from es un paquete npm que es un plugin fastify para reenviar la petici\u00f3n http actual a otro servidor.\u0026#xa0;En fastify-reply-from anterior a la versi\u00f3n 4.0.2, al dise\u00f1ar una URL espec\u00edfica, es posible escapar del prefijo del servicio de backend proxy.\u0026#xa0;Si la URL base del servidor proxy es \"/pub/\", el usuario espera que no sea posible acceder a \"/priv\" en el servicio de destino.\u0026#xa0;En versiones afectadas, es posible.\u0026#xa0;Esto se corrige en la versi\u00f3n 4.0.2"
    }
  ],
  "id": "CVE-2021-21321",
  "lastModified": "2026-06-17T03:35:17.573",
  "metrics": {
    "cvssMetricV2": [
      {
        "acInsufInfo": false,
        "baseSeverity": "HIGH",
        "cvssData": {
          "accessComplexity": "LOW",
          "accessVector": "NETWORK",
          "authentication": "NONE",
          "availabilityImpact": "PARTIAL",
          "baseScore": 7.5,
          "confidentialityImpact": "PARTIAL",
          "integrityImpact": "PARTIAL",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:P",
          "version": "2.0"
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        "exploitabilityScore": 10.0,
        "impactScore": 6.4,
        "obtainAllPrivilege": false,
        "obtainOtherPrivilege": false,
        "obtainUserPrivilege": false,
        "source": "nvd@nist.gov",
        "type": "Primary",
        "userInteractionRequired": false
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          "privilegesRequired": "NONE",
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          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.8,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
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          "baseScore": 10.0,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
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        "impactScore": 6.0,
        "source": "nvd@nist.gov",
        "type": "Primary"
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  "published": "2021-03-02T04:15:12.487",
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      "url": "https://www.npmjs.com/package/fastify-reply-from"
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      "source": "af854a3a-2127-422b-91ae-364da2661108",
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        "Patch",
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      "url": "https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889"
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      "tags": [
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      "url": "https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4"
    },
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      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
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        "Third Party Advisory"
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      "url": "https://www.npmjs.com/package/fastify-reply-from"
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  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "fastify-reply-from"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2021-21321"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-03-02T03:32:13Z",
    "nvd_published_at": "2021-03-02T04:15:00Z",
    "severity": "CRITICAL"
  },
  "details": "### Impact\n\nBy crafting a specific URL, it is possible to escape the prefix of the proxied backend service.\nIf the base url of the proxied server is `/pub/`, a user expect that accessing `/priv` on the target service would not be possible. Unfortunately, it is.\n\n[CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N)\n\n### Patches\n\nA patch have been submitted by Corey Farrell git@cfware.com, the reporter.\nAll releases after v4.0.2 include the fix.\n\n### Workarounds\n\nThere are no workaround available.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [fastify-reply-from](https://github.com/fastify/fastify-reply-from)\n* Email us at [hello@matteocollina.com](mailto:hello@matteocollina.com)",
  "id": "GHSA-qmw8-3v4g-gwj4",
  "modified": "2021-03-02T03:32:13Z",
  "published": "2021-03-03T01:52:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-21321"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889"
    },
    {
      "type": "WEB",
      "url": "https://www.npmjs.com/package/fastify-reply-from"
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  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Prefix escape"
}

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