Vulnerability-Lookup

GHSA-XP6X-3PCM-F3PH

Vulnerability from github – Published: 2026-09-24 12:31 – Updated: 2026-09-24 15:31

Details

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.

Severity

5.1 (Medium)


                  
                    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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-4637"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-24T10:17:37Z",
    "severity": "MODERATE"
  },
  "details": "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\u0027s session cookie, potentially leading to session hijacking.",
  "id": "GHSA-xp6x-3pcm-f3ph",
  "modified": "2026-09-24T15:31:29Z",
  "published": "2026-09-24T12:31:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4637"
    },
    {
      "type": "WEB",
      "url": "https://paessler.freshdesk.com/en/support/solutions/articles/76000088640"
    },
    {
      "type": "WEB",
      "url": "https://r.sec-consult.com/paessler"
    },
    {
      "type": "WEB",
      "url": "https://sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessler-prtg-network-monitor"
    },
    {
      "type": "WEB",
      "url": "https://www.paessler.com/de/download"
    },
    {
      "type": "WEB",
      "url": "https://www.paessler.com/prtg/prtg-network-monitor"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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/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",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-4637 (GCVE-0-2026-4637)

Vulnerability from cvelistv5 – Published: 2026-09-24 10:05 – Updated: 2026-09-24 12:20

Title

Reflected Cross-Site Scripting via URL Path in Paessler PRTG Network Monitor

Summary

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. 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.

Severity

5.1 (Medium)


                        
                          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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-24 12:19 UTC

CWE

CWE-79 - Improper neutralization of input during web page generation ('cross-site scripting')

Assigner

SEC-VLab mitre root

References

5 references

URL	Tags
https://paessler.freshdesk.com/en/support/solutio…	vendor-advisory
https://www.paessler.com/de/download/	patch
https://www.paessler.com/prtg/prtg-network-monitor	product
https://r.sec-consult.com/paessler	third-party-advisory
https://sec-consult.com/vulnerability-lab/advisor…	exploit

Impacted products

1 product

Vendor	Product	Version
Paessler GmbH	PRTG Network Monitor	Affected: 0 , < 26.2.120.1449 (custom)

Credits

J. Kruchem, SEC Consult Vulnerability Lab S. Michlits, SEC Consult Vulnerability Lab

Show details on NVD website

JSON

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  "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"
            }
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        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-24T12:20:41.854Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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            "tags": [
              "exploit"
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            "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": [
            {
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              "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": [
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          "lang": "en",
          "supportingMedia": [
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              "base64": false,
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              "value": "\u003cdiv\u003e\u003cspan\u003ePaessler 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.\u003c/span\u003e\u003c/div\u003e\u003cdiv\u003e\u003cspan\u003e\u003cbr\u003e\u003c/span\u003e\u003c/div\u003e\u003cdiv\u003eAn 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\u0027s session cookie, potentially leading to session hijacking.\u003c/div\u003e"
            }
          ],
          "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\u0027s session cookie, potentially leading to session hijacking."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-591",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-591 Reflected XSS"
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          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.1,
            "baseSeverity": "MEDIUM",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
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            "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",
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            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
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          "scenarios": [
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              "lang": "en",
              "type": "CWE"
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      "providerMetadata": {
        "dateUpdated": "2026-09-24T10:05:06.998Z",
        "orgId": "551230f0-3615-47bd-b7cc-93e92e730bbf",
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        },
        {
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        },
        {
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://r.sec-consult.com/paessler"
        }
      ],
      "solutions": [
        {
          "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"
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    "assignerShortName": "SEC-VLab",
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    "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"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-XP6X-3PCM-F3PH

CVE-2026-4637 (GCVE-0-2026-4637)

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