CVE-2026-4637: Paessler PRTG Network Monitor · Cross-site Scripting
Affects Paessler PRTG Network MonitorSource CVE Database V5
Not known to be exploited · CVSS 5.1 Medium : upgrade to 26.2.120.1449 when convenient.
Data as of 7 Nov 2026, 23:24 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 26.2.120.1449
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 24 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 8 Nov 2026.
What to do
Upgrade Paessler PRTG Network Monitor to 26.2.120.1449.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Paessler GmbHPRTG Network Monitor | Affected
| Fixed in
|
AI-suggested
A fixed version 26.2.120.1449 or later addresses this vulnerability. Users should upgrade to version 26.2.120.1449 or later to remediate this issue. Until then, caution should be exercised when clicking on URLs pointing to non-existent ".htm" resources on the PRTG web interface.
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.
References
- paessler.freshdesk.com/en/support/solutions/articles/76000088640 (opens in a new tab)
- paessler.com/de/download/ (opens in a new tab)
- paessler.com/prtg/prtg-network-monitor (opens in a new tab)
- r.sec-consult.com/paessler (opens in a new tab)
- sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-paessler-prtg-network-monitor/ (opens in a new tab)