What is CVE-2026-48550?

CVE-2026-48550 is Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter. The supplied enrichment data classifies it as Injection mapped to CWE-79 Cross-site Scripting.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Exploitation is reported, but no independent confirmation is available in the sources we have. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-48550 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

12 public PoC repositories reported; 2 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS, database audit logs where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-48550 using CVSS 6.1, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

mediumInjectionpublic exploit

CVE-2026-48550

CVE-2026-48550 — Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter

Nagios Core before 4.5.14 and Nagios XI before 2026R1.7 are vulnerable to reflected cross-site scripting in cmd.cgi via the NagFormId parameter. An unauthenticated remote attacker can craft a malicious link that, when followed by an authenticated user, executes arbitrary JavaScript in the victim's browser.

Published Aug 12, 2026Updated Aug 12, 2026Sources: NVD, Nagios Enterprises, LLC. (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Reported

not confirmed by CISA

EPSS

ahead of 0% of scored CVEs

Affects

Nagios Enterprises, LLC.

2 products listed

CVSS base

6.1

medium · 2 sources

Remediation

The vendor's own words where we have them.

Upgrade Nagios Core to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Nagios Enterprises, LLC.	Nagios Core	0 to < 4.5.14	Vulnerable
Nagios Enterprises, LLC.	Nagios XI	0 to < 2026R1.7	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

None

Confidentiality

Low

Integrity

Low

Scope

Changed

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

Required

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
6.1	CVSS 3.1	medium	2.8	2.7	NVD, Nagios Enterprises, LLC. (CNA), GHSA
5.1	CVSS 4.0	medium	—	—	Nagios Enterprises, LLC. (CNA)

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weakness & attack patterns

CWE-79Cross-site Scripting

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-85 · AJAX FingerprintingCAPEC-591 · Reflected XSSCAPEC-63 · Cross-Site Scripting (XSS)CAPEC-209 · XSS Using MIME Type MismatchCAPEC-592 · Stored XSSCAPEC-588 · DOM-Based XSS

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

2 of the 5 sampled are weaponized

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable Nagios Core, Nagios XI.
Monitor for scanner or exploit-pattern traffic after 12 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPSdatabase audit logs

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 6.1 (AV:N)
Aug 12, 2026 · NVD
Initial · CVE published
Aug 12, 2026 · NVD
Added · GHSA-hc96-98mh-7j3h published (medium)
Aug 12, 2026 · GitHub Security Advisory

Source activity

Readings a source repeats on a schedule, counted rather than listed.

1×CVE modified by NIST, Cweid, Description, Published, Modified, LinkAug 12, 2026 · SOCRadar CTI

References

5 on the record

github.com/NagiosEnterprises/nagioscore/blob/master/Changelog
Exploit, Third Party Advisory, NIST
www.nagios.com/security-disclosures/nagios-core/
Vendor Advisory, NIST
www.vulncheck.com/advisories/nagios-core-xi-cmd-cgi-reflected-xss-via-nagformid-parameter
Vendor Advisory, NIST
nvd.nist.gov/vuln/detail/CVE-2026-48550
NVD
github.com/advisories/GHSA-hc96-98mh-7j3h
Exploit, Third Party Advisory

Elsewhere on this site

Nagios Enterprises, LLC.every CVE for this vendor
Injectionsame class
CWE-79other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-48550 is Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter, a medium vulnerability affecting Nagios Core, Nagios XI from Nagios Enterprises, LLC.. The current evidence does not list it in CISA KEV, and the exploit status is: Exploitation is reported, but no independent confirmation is available in the sources we have. Public exploit evidence is: 12 public PoC repositories reported; 2 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 6.1 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.