CVE-2026-4637

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

• https://paessler.freshdesk.com/en/support/solutions/articles/76000088640 551230f0-3615-47bd-b7cc-93e92e730bbf
• https://r.sec-consult.com/paessler 551230f0-3615-47bd-b7cc-93e92e730bbf
• https://sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessler-prtg-network-monitor/ 134c704f-9b21-4f2e-91b3-4a467353bcc0
• https://www.paessler.com/de/download/ 551230f0-3615-47bd-b7cc-93e92e730bbf
• https://www.paessler.com/prtg/prtg-network-monitor 551230f0-3615-47bd-b7cc-93e92e730bbf

The full cvelistV5 record. Download as CVE-2026-4637.json.

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-4637",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-24T12:19:37.419469Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-24T12:20:41.854Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessler-prtg-network-monitor/"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "PRTG Network Monitor",
          "vendor": "Paessler GmbH",
          "versions": [
            {
              "lessThan": "26.2.120.1449",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "J. Kruchem, SEC Consult Vulnerability Lab"
        },
        {
          "lang": "en",
          "type": "finder",
          "value": "S. Michlits, SEC Consult Vulnerability Lab"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "<div><span>Paessler PRTG Network Monitor before version 26.2.120.1449 is affected by a reflected Cross-Site Scripting (XSS) vulnerability. When a request is made for a non-existent resource ending in \\\".htm\\\", the web interface returns an HTTP 403 \\\"Forbidden Path\\\" error page that echoes the requested URL path into the HTML response body without proper output encoding or sanitization.</span></div><div><span><br></span></div><div>An unauthenticated, remote attacker can craft a URL containing an HTML/JavaScript payload in the path (e.g. https:////welcome.htm) and, once a victim with an active PRTG session opens the crafted link, execute arbitrary JavaScript in the security context of the PRTG web interface. Because the PRTG session cookie is not protected with the HttpOnly attribute, successful exploitation allows the attacker to read and exfiltrate the victim's session cookie, potentially leading to session hijacking.</div>"
            }
          ],
          "value": "Paessler PRTG Network Monitor before version 26.2.120.1449 is affected by a reflected Cross-Site Scripting (XSS) vulnerability. When a request is made for a non-existent resource ending in \\\".htm\\\", the web interface returns an HTTP 403 \\\"Forbidden Path\\\" error page that echoes the requested URL path into the HTML response body without proper output encoding or sanitization.\n\n\n\n\nAn unauthenticated, remote attacker can craft a URL containing an HTML/JavaScript payload in the path (e.g. https:////welcome.htm) and, once a victim with an active PRTG session opens the crafted link, execute arbitrary JavaScript in the security context of the PRTG web interface. Because the PRTG session cookie is not protected with the HttpOnly attribute, successful exploitation allows the attacker to read and exfiltrate the victim's session cookie, potentially leading to session hijacking."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-591",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-591 Reflected XSS"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.1,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "ACTIVE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79 Improper neutralization of input during web page generation ('cross-site scripting')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-24T10:05:06.998Z",
        "orgId": "551230f0-3615-47bd-b7cc-93e92e730bbf",
        "shortName": "SEC-VLab"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://paessler.freshdesk.com/en/support/solutions/articles/76000088640"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://www.paessler.com/de/download/"
        },
        {
          "tags": [
            "product"
          ],
          "url": "https://www.paessler.com/prtg/prtg-network-monitor"
        },
        {
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://r.sec-consult.com/paessler"
        }
      ],
      "solutions": [
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          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Upgrade to Paessler PRTG Network Monitor version 26.2.120.1449 or later."
            }
          ],
          "value": "Upgrade to Paessler PRTG Network Monitor version 26.2.120.1449 or later."
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "Reflected Cross-Site Scripting via URL Path in Paessler PRTG Network Monitor",
      "x_generator": {
        "engine": "Vulnogram 1.0.5"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "551230f0-3615-47bd-b7cc-93e92e730bbf",
    "assignerShortName": "SEC-VLab",
    "cveId": "CVE-2026-4637",
    "datePublished": "2026-09-24T10:05:06.998Z",
    "dateReserved": "2026-03-23T10:31:35.511Z",
    "dateUpdated": "2026-09-24T12:20:41.854Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}