CVE-2021-25299

CRITICALNVD 6.19.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because EPSS predicts 98% probability of exploitation within the next 30 days (99th percentile of EPSS-scored CVEs). NVD baseline CVSS 6.1 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, nvd
Elevated
9.0EG
EchelonGraph verdictMitigate this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 98%
CISA-KEV: Not listedEPSS PROB: 98%CVSS: 6.1Exploit: Elevated riskExposed services: Not assessed

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

Nagios XI version xi-5.7.5 is affected by cross-site scripting (XSS). The vulnerability exists in the file /usr/local/nagiosxi/html/admin/sshterm.php due to improper sanitization of user-controlled input. A maliciously crafted URL, when clicked by an admin user, can be used to steal his/her session cookies or it can be chained with the previous bugs to get one-click remote command execution (RCE) on the Nagios XI server.

CVSS v3
6.1
EG Score
9.0CRITICALhigh confidence
EG Risk
84
EG Risk 84/100CISA 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
Severity90% × 45%
Exploitation98% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track* or 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
98%
EPSS %ILE
99th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* or 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 (EG-KEV: elevated) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). 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

February 15, 2021

Last Modified

July 9, 2026

Advisory Details (2)

Auto-updated Jul 9, 2026
No fix on record yet.
generic

nagios-xi-5.7.5-bugs/README.md at main · fs0c-sh/nagios-xi-5.7.5-bugs · GitHub

https://github.com/fs0c-sh/nagios-xi-5.7.5-bugs/blob/main/README.md
generic

Nagios XI Versions

https://assets.nagios.com/downloads/nagiosxi/versions.php

Vendor Advisories for CVE-2021-25299(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 3× in last 7d / 9× 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. 2026-10-03 14:22 UTCEPSS rescore
  2. 2026-10-03 14:22 UTCEPSS rescore
  3. 2026-09-30 15:32 UTCEG score recompute
  4. 2026-09-24 14:00 UTCEPSS rescore
  5. 2026-09-21 20:28 UTCEPSS rescore
  6. 2026-09-18 19:23 UTCEPSS rescore
  7. 2026-09-17 19:23 UTCEPSS rescore
  8. 2026-09-17 19:23 UTCEPSS rescore
  9. 2026-09-06 13:44 UTCEPSS rescore
  10. 2026-09-05 15:25 UTCEPSS rescore
  11. 2026-08-30 19:14 UTCEPSS rescore
  12. 2026-08-30 01:19 UTCEPSS rescore
  13. 2026-08-26 14:42 UTCEPSS rescore
  14. 2026-08-24 14:12 UTCEPSS rescore
  15. 2026-08-19 17:01 UTCEPSS rescore
  16. 2026-08-18 13:45 UTCEPSS rescore
  17. 2026-08-17 13:44 UTCEPSS rescore
  18. 2026-08-12 13:47 UTCEPSS rescore
  19. 2026-07-30 16:25 UTCEPSS rescore
  20. 2026-07-30 16:25 UTCEPSS rescore
  21. 2026-07-30 01:28 UTCEPSS rescore
  22. 2026-07-30 01:27 UTCEPSS rescore
  23. 2026-07-28 15:33 UTCEPSS rescore
  24. 2026-07-26 14:52 UTCEPSS rescore
  25. 2026-07-26 14:52 UTCEPSS rescore
Show 42 more
  1. 2026-07-23 01:58 UTCEG score recompute
  2. 2026-07-22 22:45 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-22 14:06 UTCEPSS rescore
  5. 2026-07-09 02:55 UTCNVD updateCVSS v3 → 6.1 · severity → MEDIUM
  6. 2026-07-09 01:24 UTCMITRE cvelistV5
  7. 2026-07-08 15:12 UTCEPSS rescore
  8. 2026-07-07 13:43 UTCEPSS rescore
  9. 2026-07-05 02:28 UTCEPSS rescore
  10. 2026-07-05 00:28 UTCNVD updateCVSS v3 → 6.1 · severity → MEDIUM
  11. 2026-07-04 23:57 UTCMITRE cvelistV5
  12. 2026-07-02 16:57 UTCEPSS rescore
  13. 2026-06-30 23:20 UTCEPSS rescore
  14. 2026-06-30 23:20 UTCEPSS rescore
  15. 2026-06-27 03:06 UTCEPSS rescore
  16. 2026-06-27 03:06 UTCEPSS rescore
  17. 2026-06-23 21:31 UTCEPSS rescore
  18. 2026-06-23 21:31 UTCEPSS rescore
  19. 2026-06-19 19:24 UTCEPSS rescore
  20. 2026-06-19 19:24 UTCEPSS rescore
  21. 2026-06-15 17:46 UTCEPSS rescore
  22. 2026-06-12 23:10 UTCEPSS rescore
  23. 2026-06-10 22:16 UTCEPSS rescore
  24. 2026-06-10 13:20 UTCEPSS rescore
  25. 2026-06-08 14:15 UTCEPSS rescore
  26. 2026-06-07 15:23 UTCEPSS rescore
  27. 2026-06-07 15:23 UTCEPSS rescore
  28. 2026-06-06 13:46 UTCEPSS rescore
  29. 2026-06-06 13:46 UTCEPSS rescore
  30. 2026-06-06 13:46 UTCEPSS rescore
  31. 2026-06-05 22:45 UTCEPSS rescore
  32. 2026-06-05 22:45 UTCEPSS rescore
  33. 2026-05-31 22:29 UTCEPSS rescore
  34. 2026-05-31 22:29 UTCEPSS rescore
  35. 2026-05-31 00:15 UTCEPSS rescore
  36. 2026-05-29 13:42 UTCEPSS rescore
  37. 2026-05-28 13:43 UTCEPSS rescore
  38. 2026-05-28 13:43 UTCEPSS rescore
  39. 2026-05-26 20:48 UTCEG score recompute
  40. 2026-05-26 20:48 UTCGHSA enrichment
  41. 2026-05-26 07:17 UTCEPSS rescore
  42. 2026-05-26 07:17 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2021/CVE-2021-25299.yaml
    First seen Jan 1, 2021

    Nagios XI 5.7.5 - Cross-Site Scripting

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-25299?
CVE-2021-25299 is a critical vulnerability published on February 15, 2021. Nagios XI version xi-5.7.5 is affected by cross-site scripting (XSS). The vulnerability exists in the file /usr/local/nagiosxi/html/admin/sshterm.php due to improper sanitization of user-controlled input. A maliciously crafted URL, when clicked by an admin user, can be used to steal his/her session…
When was CVE-2021-25299 disclosed?
CVE-2021-25299 was first published on February 15, 2021, with the most recent update on July 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-25299 actively exploited?
CVE-2021-25299 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98% probability of exploitation in the next 30 days (99th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-25299?
CVE-2021-25299 has a CVSS v3 base score of 6.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
How do I remediate CVE-2021-25299?
No fix for CVE-2021-25299 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-2021-25299 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-25299

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