CVE-2026-4637
Paessler PRTG Network Monitor before version 26.2.120.1449 is affected by a reflected Cross-Site Scripting (XSS) vulnerability.
Does this matter?
Lower severity and a low EPSS score (0.60%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 4.0
- 5.1 MEDIUMCVSS: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/M
- EPSS
- 0.60% probability · 48th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Source
- 551230f0-3615-47bd-b7cc-93e92e730bbf
EPSS moved from 0.6% on 25 September 2026 to 0.6% on 26 October 2026.
References
- https://paessler.freshdesk.com/en/support/solutions/articles/76000088640
- https://r.sec-consult.com/paessler
- https://www.paessler.com/de/download/
- https://www.paessler.com/prtg/prtg-network-monitor
- https://sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessler-prtg-network-monitor/
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.