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CVE-2021-34359

Status: ModifiedMedium (5.4)—

A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running Proxy Server. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) and later

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Qnap — NAS Proxy Server

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-34359",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 3.5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:S/C:N/I:P/A:N",
          "authentication": "SINGLE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "LOW",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 6.8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": true
      }
    ],
    "cvssMetricV31": [
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        "type": "Secondary",
        "source": "security@qnapsecurity.com.tw",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 6.9,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
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          "availabilityImpact": "NONE",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
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        "impactScore": 4.7,
        "exploitabilityScore": 1.7
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        "cvssData": {
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        "exploitabilityScore": 2.3
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  "affected": [
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      "source": "security@qnapsecurity.com.tw",
      "affectedData": [
        {
          "vendor": "QNAP Systems Inc.",
          "product": "Proxy Server",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "1.4.2 ( 2021/12/30 )",
              "versionType": "custom"
            }
          ],
          "platforms": [
            "QTS 4.5.x"
          ]
        }
      ]
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  ],
  "published": "2022-02-25T06:15:06.720",
  "references": [
    {
      "url": "https://www.qnap.com/en/security-advisory/qsa-22-04",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "security@qnapsecurity.com.tw"
    },
    {
      "url": "https://www.qnap.com/en/security-advisory/qsa-22-04",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security@qnapsecurity.com.tw",
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ]
    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running Proxy Server. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) and later"
    },
    {
      "lang": "es",
      "value": "Se ha informado de una vulnerabilidad de tipo cross-site scripting (XSS) que afecta al dispositivo QNAP que ejecuta Proxy Server. Si es explotado, esta vulnerabilidad permite a atacantes remotos inyectar código malicioso. Ya hemos corregido esta vulnerabilidad en las siguientes versiones de Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) y posteriores.\n"
    }
  ],
  "lastModified": "2026-06-17T03:55:43.057",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "criteria": "cpe:2.3:a:qnap:nas_proxy_server:*:*:*:*:*:*:*:*",
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              "versionEndIncluding": "4.5.4",
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            }
          ],
          "operator": "OR"
        }
      ],
      "operator": "AND"
    }
  ],
  "sourceIdentifier": "security@qnapsecurity.com.tw"
}