Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-4637

CVE-2026-4637MEDIUM

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

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   A   N   N   N    5.1   .0055   44.1     —

AFFECTED
  Product               Versions     Fixed
  PRTG Network Monitor  unspecified  —

TIMELINE
  Mar 23  Reserved by SEC-VLab
  Sep 24  EXPLOIT PUBLISHED — CVE-2026-4637 (Paessler GmbH PRTG Network Monitor). Public exploit reference added.
  Sep 24  Published (CNA: SEC-VLab)

CWE-79 · CNA: SEC-VLab · CVSS v4.0 · 5 references · NVD status: Deferred

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
March 23, 2026	Reserved	Reserved by SEC-VLab
September 24, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-4637 (Paessler GmbH PRTG Network Monitor). Public exploit reference added.
September 24, 2026	Published	Published (CNA: SEC-VLab)

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Paessler GmbH	PRTG Network Monitor	—	—	—

Weaknesses

CWE-79

References (5)

Authoritative record: CVE-2026-4637 at cve.org

Vendors: paessler

Weaknesses: CWE-79

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-4637 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.