Reflected Cross-Site Scripting via URL Path in Paessler PRTG Network Monitor
Summary
| CVE | CVE-2026-4637 |
|---|---|
| State | PUBLISHED |
| Assigner | SEC-VLab |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-24 10:17:37 UTC |
| Updated | 2026-09-24 20:43:32 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 5.1 MEDIUM from 551230f0-3615-47bd-b7cc-93e92e730bbf
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
EPSS: 0.005520000 probability, percentile 0.437460000 (date 2026-09-25)
Problem Types: CWE-79 | CWE-79 CWE-79 Improper neutralization of input during web page generation ('cross-site scripting')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 551230f0-3615-47bd-b7cc-93e92e730bbf | Secondary | 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/E:X/C... |
| 4.0 | CNA | CVSS | 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 |
CVSS v4.0 Breakdown
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
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Paessler GmbH | PRTG Network Monitor | affected 26.2.120.1449 custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.paessler.com/prtg/prtg-network-monitor | 551230f0-3615-47bd-b7cc-93e92e730bbf | www.paessler.com | |
| paessler.freshdesk.com/en/support/solutions/articles/76000088640 | 551230f0-3615-47bd-b7cc-93e92e730bbf | paessler.freshdesk.com | |
| www.paessler.com/de/download | 551230f0-3615-47bd-b7cc-93e92e730bbf | www.paessler.com | |
| r.sec-consult.com/paessler | 551230f0-3615-47bd-b7cc-93e92e730bbf | r.sec-consult.com | |
| sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessl... | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | sec-consult.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: J. Kruchem, SEC Consult Vulnerability Lab (en)
CNA: S. Michlits, SEC Consult Vulnerability Lab (en)
Additional Advisory Data
Solutions
CNA: Upgrade to Paessler PRTG Network Monitor version 26.2.120.1449 or later.