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

Paessler GmbH PRTG Network Monitor · CVE-2026-4637
0 news outlets0 CERTs and agencies0 researchers

Assessment: Track

SSVC decision points: exploitation poc, automatable yes, technical impact partial, deployment low.

What is it?

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.

Evidence

Technical advisories (1)
Detailed write-ups from security research teams

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
5.1
EPSS
0.6%
First seen
2 h ago
Status
confirmed

All Paessler GmbH vulnerabilities