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CVE-2021-34823

Estado: ModificadaCrítica (9.1)—

The ON24 ScreenShare (aka DesktopScreenShare.app) plugin before 2.0 for macOS allows remote file access via its built-in HTTP server. This allows unauthenticated remote users to retrieve files accessible to the logged-on macOS user. When a remote user sends a crafted HTTP request to the server, it triggers a code path that will download a configuration file from a specified remote machine over HTTP. There is an XXE flaw in processing of this configuration file that allows reading local (to macOS) files and uploading them to remote machines.

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)

On24 — Screenshare

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-34823",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 4.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.1,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-08-13T17:15:16.527",
  "references": [
    {
      "url": "https://www.trustwave.com/en-us/resources/security-resources/security-advisories/",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=29105",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://www.trustwave.com/en-us/resources/security-resources/security-advisories/",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=29105",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-611"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The ON24 ScreenShare (aka DesktopScreenShare.app) plugin before 2.0 for macOS allows remote file access via its built-in HTTP server. This allows unauthenticated remote users to retrieve files accessible to the logged-on macOS user. When a remote user sends a crafted HTTP request to the server, it triggers a code path that will download a configuration file from a specified remote machine over HTTP. There is an XXE flaw in processing of this configuration file that allows reading local (to macOS) files and uploading them to remote machines."
    },
    {
      "lang": "es",
      "value": "El plugin ON24 ScreenShare (también se conoce como DesktopScreenShare.app) versiones anteriores a 2.0 para macOS permite el acceso remoto a archivos por medio de su servidor HTTP incorporado. Esto permite a usuarios remotos no autenticados recuperar archivos accesibles para el usuario de macOS que ha iniciado la sesión. Cuando un usuario remoto envía una petición HTTP diseñada al servidor, desencadena una ruta de código que descargará un archivo de configuración de una máquina remota especificada a través de HTTP. Se presenta un fallo de tipo XXE en el procesamiento de este archivo de configuración que permite leer archivos locales (para macOS) y cargarlos en máquinas remotas."
    }
  ],
  "lastModified": "2026-06-17T03:56:37.763",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:on24:screenshare:*:*:*:*:*:macos:*:*",
              "vulnerable": true,
              "matchCriteriaId": "686D66ED-B4D7-4770-B983-5D2FF7E2AE2E",
              "versionEndExcluding": "2.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}