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 (top 0.1% of all 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 verdictPatch 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: 0

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

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
9.0(high)
EG Risk
84(Track)
EG Risk 84/100SSVC: Track

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%
Action: Routine — remediate on your standard cadence.
EPSS PROB
98%
EPSS %ILE
100%
KEV
Not listed

Published

February 15, 2021

Last Modified

July 9, 2026

Advisory Details (2)

Auto-updated Jul 9, 2026
No patch confirmed 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 / 15× 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. 2026-08-19 17:01 UTCEPSS rescore
  2. 2026-08-18 13:45 UTCEPSS rescore
  3. 2026-08-17 13:44 UTCEPSS rescore
  4. 2026-08-12 13:47 UTCEPSS rescore
  5. 2026-07-30 16:25 UTCEPSS rescore
  6. 2026-07-30 16:25 UTCEPSS rescore
  7. 2026-07-30 01:28 UTCEPSS rescore
  8. 2026-07-30 01:27 UTCEPSS rescore
  9. 2026-07-28 15:33 UTCEPSS rescore
  10. 2026-07-26 14:52 UTCEPSS rescore
  11. 2026-07-26 14:52 UTCEPSS rescore
  12. 2026-07-23 01:58 UTCEG score recompute
  13. 2026-07-22 22:45 UTCEG score recompute
  14. 2026-07-22 14:06 UTCEPSS rescore
  15. 2026-07-22 14:06 UTCEPSS rescore
  16. 2026-07-09 02:55 UTCNVD updateCVSS v3 → 6.1 · severity → MEDIUM
  17. 2026-07-09 01:24 UTCMITRE cvelistV5
  18. 2026-07-08 15:12 UTCEPSS rescore
  19. 2026-07-07 13:43 UTCEPSS rescore
  20. 2026-07-05 02:28 UTCEPSS rescore
  21. 2026-07-05 00:28 UTCNVD updateCVSS v3 → 6.1 · severity → MEDIUM
  22. 2026-07-04 23:57 UTCMITRE cvelistV5
  23. 2026-07-02 16:57 UTCEPSS rescore
  24. 2026-06-30 23:20 UTCEPSS rescore
  25. 2026-06-30 23:20 UTCEPSS rescore
Show 28 more
  1. 2026-06-27 03:06 UTCEPSS rescore
  2. 2026-06-27 03:06 UTCEPSS rescore
  3. 2026-06-23 21:31 UTCEPSS rescore
  4. 2026-06-23 21:31 UTCEPSS rescore
  5. 2026-06-19 19:24 UTCEPSS rescore
  6. 2026-06-19 19:24 UTCEPSS rescore
  7. 2026-06-15 17:46 UTCEPSS rescore
  8. 2026-06-12 23:10 UTCEPSS rescore
  9. 2026-06-10 22:16 UTCEPSS rescore
  10. 2026-06-10 13:20 UTCEPSS rescore
  11. 2026-06-08 14:15 UTCEPSS rescore
  12. 2026-06-07 15:23 UTCEPSS rescore
  13. 2026-06-07 15:23 UTCEPSS rescore
  14. 2026-06-06 13:46 UTCEPSS rescore
  15. 2026-06-06 13:46 UTCEPSS rescore
  16. 2026-06-06 13:46 UTCEPSS rescore
  17. 2026-06-05 22:45 UTCEPSS rescore
  18. 2026-06-05 22:45 UTCEPSS rescore
  19. 2026-05-31 22:29 UTCEPSS rescore
  20. 2026-05-31 22:29 UTCEPSS rescore
  21. 2026-05-31 00:15 UTCEPSS rescore
  22. 2026-05-29 13:42 UTCEPSS rescore
  23. 2026-05-28 13:43 UTCEPSS rescore
  24. 2026-05-28 13:43 UTCEPSS rescore
  25. 2026-05-26 20:48 UTCEG score recompute
  26. 2026-05-26 20:48 UTCGHSA enrichment
  27. 2026-05-26 07:17 UTCEPSS rescore
  28. 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 in the National Vulnerability Database 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, which ranks it in the top 0.1% of all 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.
How do I remediate CVE-2021-25299?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-25299, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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