Security readout for executives and security teams
Plain-English summary
Older versions of Nagios Fusion, a tool that monitors IT systems, do not properly clean up text entered on its Users and Servers pages. A logged-in user could plant content that runs in another user's browser when they view those pages, potentially hijacking sessions or showing fake content. Upgrading to Fusion 4.0.1 fixes the issue.
Executive priority
Schedule a routine upgrade to Nagios Fusion 4.0.1 or later during the next maintenance window; treat as standard hygiene unless the console is internet-facing.
Technical view
Nagios Fusion versions prior to 4.0.1 fail to properly validate or escape user-supplied input rendered on the Users and Servers pages, enabling cross-site scripting (CWE-79). An authenticated low-privilege actor can inject script that executes in a victim's browser session, potentially leading to session theft, forced actions, or UI tampering within the Fusion management console.
Likely exposure
Organizations running Nagios Fusion versions earlier than 4.0.1, especially where the management console is reachable by multiple staff or exposed beyond a trusted network. Monitoring teams that share Fusion accounts or that allow low-privilege users to edit user or server entries face the highest exposure.
Exploitation context
No public reports of active exploitation and the CVE is not on CISA's KEV list. The CVSS vector indicates an authenticated attacker with low privileges who can persuade another user to load a crafted page or link, suggesting an insider or compromised-account scenario rather than mass exploitation.
Researcher notes
CWE-79 stored or reflected XSS in authenticated admin pages (Users and Servers). CVSS 4.0 vector AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N indicates impact crosses to a different security scope (the victim's browser session). Vendor changelog identifies 4.0.1 as the fix; VulnCheck advisory provides third-party context. No public PoC or KEV entry observed in the provided sources.
Mitigation direction
- Upgrade Nagios Fusion to version 4.0.1 or later per vendor changelog.
- Restrict Fusion console access to trusted networks or VPN until patched.
- Limit who can create or edit users and server entries to vetted admins.
- Review vendor advisories for any additional configuration guidance.
Validation and detection
- Inventory all Nagios Fusion deployments and record exact installed versions.
- Compare versions against the 4.0.1 fix line in the vendor changelog.
- Confirm whether the Fusion console is exposed beyond trusted management networks.
- Audit user accounts and roles able to access Users and Servers pages.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2017-20209 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.1 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
5.1MediumVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.nagios.com/changelog/nagios-fusion/CVE reference · release-notes, patch
- https://www.vulncheck.com/advisories/nagios-fusion-xss-via-users-servers-pageCVE reference · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.