CVE-2026-4637

MEDIUMPre-NVD 5.15.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (44th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this weekElevated
5.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 5.1Exploit: Elevated riskExposed services: Not assessed

No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.

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 v3
5.1
EG Score
5.1MEDIUMmedium confidence
EG Risk
54
EG Risk 54/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity51% × 45%
Exploitation40% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.6%
EPSS %ILE
44th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 24, 2026

Last Modified

September 24, 2026

Advisory Details (3)

Auto-updated Sep 24, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic

PRTG Network Monitor – All-in-one network monitoring tool

https://www.paessler.com/prtg/prtg-network-monitor
generic

SEC Consult - a leading consultant in application and cybersecurity as well as IT security

https://r.sec-consult.com/paessler
generic🟡 PoC Available

Vulnerabilities in PRTG prior v26.2.120.1449 | Paessler Knowledge Base

https://paessler.freshdesk.com/en/support/solutions/articles/76000088640

Vendor Advisories for CVE-2026-4637(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 17× in last 7d / 33× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-04 18:23 UTCGHSA enrichment
  3. 2026-10-03 18:39 UTCEG score recompute
  4. 2026-10-03 18:39 UTCGHSA enrichment
  5. 2026-10-03 14:25 UTCEPSS rescore
  6. 2026-10-02 18:48 UTCEG score recompute
  7. 2026-10-02 18:48 UTCGHSA enrichment
  8. 2026-10-01 19:50 UTCEPSS rescore
  9. 2026-10-01 19:04 UTCGHSA enrichment
  10. 2026-09-30 19:22 UTCEG score recompute
  11. 2026-09-30 19:22 UTCGHSA enrichment
  12. 2026-09-30 15:03 UTCEPSS rescore
  13. 2026-09-29 19:40 UTCEG score recompute
  14. 2026-09-29 19:40 UTCGHSA enrichment
  15. 2026-09-28 19:51 UTCEG score recompute
  16. 2026-09-28 19:51 UTCGHSA enrichment
  17. 2026-09-28 13:51 UTCEPSS rescore
  18. 2026-09-27 20:06 UTCEG score recompute
  19. 2026-09-27 20:06 UTCGHSA enrichment
  20. 2026-09-27 13:48 UTCEPSS rescore
  21. 2026-09-26 20:24 UTCEG score recompute
  22. 2026-09-26 20:24 UTCGHSA enrichment
  23. 2026-09-26 15:59 UTCEPSS rescore
  24. 2026-09-26 00:27 UTCEPSS rescore
  25. 2026-09-25 20:40 UTCGHSA enrichment
Show 8 more
  1. 2026-09-24 20:55 UTCGHSA enrichment
  2. 2026-09-24 13:24 UTCEG score recompute
  3. 2026-09-24 13:24 UTCGHSA enrichment
  4. 2026-09-24 12:47 UTCEG score recompute
  5. 2026-09-24 12:47 UTCGHSA enrichment
  6. 2026-09-24 10:19 UTCEG score recompute
  7. 2026-09-24 10:14 UTCEG score recompute
  8. 2026-09-24 10:14 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-4637?
CVE-2026-4637 is a medium vulnerability published on September 24, 2026. 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…
When was CVE-2026-4637 disclosed?
CVE-2026-4637 was first published on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-4637 actively exploited?
CVE-2026-4637 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-4637?
CVE-2026-4637 has a CVSS base score of 5.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-4637?
No fix for CVE-2026-4637 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-4637 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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