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CVE-2026-49756

Estado: AnalizadaBaja (2.1)—

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata.

Req.Utils.encode_form_part/2 in lib/req/utils.ex builds the per-part headers by interpolating the caller-supplied name, filename, and content_type values directly into the content-disposition and content-type lines with no escaping or CRLF stripping. A value containing ", \r, or \n closes the surrounding quoted value and starts a new header line; an additional \r\n--<boundary> terminates the current part and prepends a smuggled part of the attacker's choosing.

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This is reachable through every supported way of supplying a part. It is particularly easy when value is a %File.Stream{}, because filename then defaults to Path.basename(stream.path) and POSIX filenames may legitimately contain \r and \n. Any application that forwards user-controlled filenames (or field names / MIME types) through Req.post/2 with form_multipart: lets an attacker inject arbitrary headers into the outgoing multipart body or smuggle additional fields and parts into the request the victim service sends downstream.

This issue affects req: from 0.5.3 before 0.6.0.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Wojtekmach — REQ

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-49756",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-49756",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-06-08T16:05:54.070488Z"
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        "source": "nvd@nist.gov",
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          "attackVector": "NETWORK",
          "baseSeverity": "LOW",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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    "cvssMetricV40": [
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        "type": "Secondary",
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        "cvssData": {
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          "version": "4.0",
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          "Automatable": "NOT_DEFINED",
          "attackVector": "LOCAL",
          "baseSeverity": "LOW",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
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          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "LOW",
          "vulnIntegrityImpact": "LOW",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
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          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "LOW",
          "vulnConfidentialityImpact": "NONE",
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          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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      "affectedData": [
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          "modules": [
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          "versions": [
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          "packageURL": "pkg:hex/req",
          "packageName": "req",
          "programFiles": [
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          ],
          "collectionURL": "https://repo.hex.pm",
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          "programRoutines": [
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            }
          ]
        },
        {
          "cpes": [
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          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
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              "name": "'Elixir.Req.Utils':encode_form_part/2"
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          ]
        }
      ]
    }
  ],
  "published": "2026-06-08T16:16:44.040",
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-49756.html",
      "tags": [
        "Third Party Advisory",
        "Mitigation"
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
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      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-49756",
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        "Third Party Advisory"
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
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      "url": "https://github.com/wojtekmach/req/security/advisories/GHSA-px9f-whj3-246m",
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      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "description": [
        {
          "lang": "en",
          "value": "CWE-93"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata.\n\nReq.Utils.encode_form_part/2 in lib/req/utils.ex builds the per-part headers by interpolating the caller-supplied name, filename, and content_type values directly into the content-disposition and content-type lines with no escaping or CRLF stripping. A value containing \", \\r, or \\n closes the surrounding quoted value and starts a new header line; an additional \\r\\n--<boundary> terminates the current part and prepends a smuggled part of the attacker's choosing.\n\nThis is reachable through every supported way of supplying a part. It is particularly easy when value is a %File.Stream{}, because filename then defaults to Path.basename(stream.path) and POSIX filenames may legitimately contain \\r and \\n. Any application that forwards user-controlled filenames (or field names / MIME types) through Req.post/2 with form_multipart: lets an attacker inject arbitrary headers into the outgoing multipart body or smuggle additional fields and parts into the request the victim service sends downstream.\n\nThis issue affects req: from 0.5.3 before 0.6.0."
    },
    {
      "lang": "es",
      "value": "La vulnerabilidad de Neutralización Incorrecta de Secuencias CRLF ('Inyección CRLF') en wojtekmach Req permite el contrabando de parámetros multipart a través de metadatos de parte influenciados por el atacante.\n\nReq.Utils.encode_form_part/2 en lib/req/utils.ex construye los encabezados por parte interpolando los valores de nombre, nombre de archivo y tipo de contenido suministrados por el llamador directamente en las líneas de content-disposition y content-type sin escape ni eliminación de CRLF. Un valor que contiene \", \\r, o \\n cierra el valor entre comillas circundante y comienza una nueva línea de encabezado; un \\r\\n--<boundary> adicional termina la parte actual y antepone una parte contrabandeada a elección del atacante.\n\nEsto es alcanzable a través de cada forma compatible de suministrar una parte. Es particularmente fácil cuando el valor es un %File.Stream{}, porque el nombre de archivo por defecto es Path.basename(stream.path) y los nombres de archivo POSIX pueden contener legítimamente \\r y \\n. Cualquier aplicación que reenvíe nombres de archivo controlados por el usuario (o nombres de campo / tipos MIME) a través de Req.post/2 con form_multipart: permite a un atacante inyectar encabezados arbitrarios en el cuerpo multipart saliente o contrabandear campos y partes adicionales en la solicitud que el servicio víctima envía aguas abajo.\n\nEste problema afecta a req: desde 0.5.3 antes de 0.6.0."
    }
  ],
  "lastModified": "2026-08-18T19:15:38.860",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E3441D9F-1ACB-44AD-905C-F62F2A15C275",
              "versionEndExcluding": "0.6.0",
              "versionStartIncluding": "0.5.3"
            }
          ],
          "operator": "OR"
        }
      ]
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  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}