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CVE-2017-20203

Estado: AplazadaCrítica (9.3)—

NetSarang Xmanager Enterprise 5.0 Build 1232, Xmanager 5.0 Build 1045, Xshell 5.0 Build 1322, Xftp 5.0 Build 1218, and Xlpd 5.0 Build 1220 contain a malicious nssock2.dll that implements a multi-stage, DNS-based backdoor. The dormant library contacts a C2 DNS server via a specially crafted TXT record for a month‑generated domain. After receiving a decryption key, it then downloads and executes arbitrary code, creates an encrypted virtual file system (VFS) in the registry, and grants the attacker full remote code execution, data exfiltration, and persistence.

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NetSarang released builds for each product line that remediated the compromise: Xmanager Enterprise Build 1236, Xmanager Build 1049, Xshell Build 1326, Xftp Build 1222, and Xlpd Build 1224. Kaspersky Lab identified an instance of exploitation in the wild in August 2017.

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).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

DLL maliciosa inyectada en cadena de suministro (builds comprometidas de NetSarang). Ejecuta código arbitrario, exfiltra datos y persiste mediante C2 DNS.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Limit Software InstallationApplication Developer GuidanceVulnerability ScanningUser Account ManagementRestrict Web-Based ContentPrivileged Account Management

Tecnologías afectadas (5)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Netsarang — XftpAINetsarang — XlpdAINetsarang — XmanagerAINetsarang — Xmanager EnterpriseAINetsarang — XshellAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2017-20203",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2017-20203",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2025-10-15T16:14:00.667763Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "disclosure@vulncheck.com",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 9.3,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/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": "ACTIVE",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "HIGH",
          "vulnConfidentialityImpact": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "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"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "disclosure@vulncheck.com",
      "affectedData": [
        {
          "vendor": "NetSarang Computer, Inc.",
          "modules": [
            "nssock2.dll"
          ],
          "product": "Xmanager Enterprise",
          "versions": [
            {
              "status": "affected",
              "version": "5.0 Build 1232"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "NetSarang Computer, Inc.",
          "modules": [
            "nssock2.dll"
          ],
          "product": "Xmanager",
          "versions": [
            {
              "status": "affected",
              "version": "5.0 Build 1045"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "NetSarang Computer, Inc.",
          "modules": [
            "nssock2.dll"
          ],
          "product": "Xshell",
          "versions": [
            {
              "status": "affected",
              "version": "5.0 Build 1322"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "NetSarang Computer, Inc.",
          "modules": [
            "nssock2.dll"
          ],
          "product": "Xftp",
          "versions": [
            {
              "status": "affected",
              "version": "5.0 Build 1218"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "NetSarang Computer, Inc.",
          "modules": [
            "nssock2.dll"
          ],
          "product": "Xlpd",
          "versions": [
            {
              "status": "affected",
              "version": "5.0 Build 1220"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2025-10-09T17:15:57.423",
  "references": [
    {
      "url": "https://securelist.com/shadowpad-in-corporate-networks/81432/",
      "source": "disclosure@vulncheck.com"
    },
    {
      "url": "https://usa.kaspersky.com/about/press-releases/shadowpad-attackers-hid-backdoor-in-software-used-by-hundreds-of-large-companies-worldwide",
      "source": "disclosure@vulncheck.com"
    },
    {
      "url": "https://web.archive.org/web/20181022035109/https://www.netsarang.com/news/security_exploit_in_july_18_2017_build.html",
      "source": "disclosure@vulncheck.com"
    },
    {
      "url": "https://www.vulncheck.com/advisories/netsarang-malicious-backdoor-supply-chain-compromise",
      "source": "disclosure@vulncheck.com"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "disclosure@vulncheck.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-506"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "NetSarang Xmanager Enterprise 5.0 Build 1232, Xmanager 5.0 Build 1045, Xshell 5.0 Build 1322, Xftp 5.0 Build 1218, and Xlpd 5.0 Build 1220 contain a malicious nssock2.dll that implements a multi-stage, DNS-based backdoor. The dormant library contacts a C2 DNS server via a specially crafted TXT record for a month‑generated domain. After receiving a decryption key, it then downloads and executes arbitrary code, creates an encrypted virtual file system (VFS) in the registry, and grants the attacker full remote code execution, data exfiltration, and persistence. NetSarang released builds for each product line that remediated the compromise: Xmanager Enterprise Build 1236, Xmanager Build 1049, Xshell Build 1326, Xftp Build 1222, and Xlpd Build 1224. Kaspersky Lab identified an instance of exploitation in the wild in August 2017."
    }
  ],
  "lastModified": "2026-06-17T01:15:24.160",
  "sourceIdentifier": "disclosure@vulncheck.com"
}