NVD / CVE Program· CNA VulnCheck

CVE-2026-48553: Nagios Core / XI Authenticated RCE via Custom-Variable Macro Injection

HighCVSS 7.7 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.96% (FIRST EPSS); higher than 62.1% of all records.
Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Nagios Enterprises, LLC. Nagios Core 4.5.13.

Low priority for now. Upgrade to Nagios Enterprises, LLC. Nagios Core 4.5.13 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Nagios Core before 4.5.13 and Nagios XI before 2026R1.5 are vulnerable to authenticated remote code execution via custom-variable macro injection through the Nagios Remote Data Processor (NRDP). When a custom variable defined on a host, service, or contact is referenced in a shell-executed command line, an authenticated attacker with NRDP access can inject OS commands through the macro value. Exploitation requires a non-default configuration in which a custom variable is defined and referenced in a shell-executed command.

Published: Aug 12, 2026
Updated: Sep 8, 2026
EPSS: 0.9% · 62th percentile
CWE: CWE-78

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.9%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · VulnCheck: 7.7; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (VulnCheck). Independent of NVD's CPE analysis and usually ahead of it.

Nagios Enterprises, LLC. Nagios Core
- before 4.5.13affected · semver
Nagios Enterprises, LLC. Nagios XI
- before 2026R1.5affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	nagios4	before 4.4.6-4+deb12u2	4.4.6-4+deb12u2
Debian:13	nagios4	before 4.4.6-4.1+deb13u2	4.4.6-4.1+deb13u2
Debian:14	nagios4	before 4.5.14+ds-1	4.5.14+ds-1

Same product

Other highest-scoring records for the same primary product.

CVE-2026-48554Nagios Core / XI Authenticated RCE via Unfiltered NOTIFICATION-Family Macro Substitution
30Monitor
CVE-2026-48549Nagios Core / XI CSRF via cmd.cgi Double-Submit Cookie
27Monitor
CVE-2026-48548Nagios Core CSRF via cmd.cgi
27Monitor

Published before and after this one in the same product

← EarlierCVE-2026-48550Aug 12, 2026 · Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter
20Monitor
← EarlierCVE-2026-48551Aug 12, 2026 · Nagios Core / XI CSRF Protection Bypass via Double-Submit Cookie
24Monitor
← EarlierCVE-2026-48552Aug 12, 2026 · Nagios Core / XI DOM-based XSS via jsonquery.js
20Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Nagios Enterprises, LLC. Nagios Core	4.5.13	Vendor (CNA)
debian:nagios4	4.4.6-4.1+deb13u2 · Debian:13	Package registry (OSV)
debian:nagios4	4.4.6-4+deb12u2 · Debian:12	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-485540 days apartNagios Core / XI Authenticated RCE via Unfiltered NOTIFICATION-Family Macro Substitution
30Monitor

Not on record for this CVE: patch commit or PR link · researcher credit · public bounty program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: X

Weakness class (CWE)

CWE-78 · Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

User input is inserted as text into a shell command. The shell may interpret special characters in the input as part of the command.

The bug in code

The whole CWE-78 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const host = req.body.host;
2exec("ping -c 1 " + host, onResult);

Fixed

1const host = req.body.host;
2if (!/^[a-z0-9.-]{1,253}$/i.test(host)) return res.sendStatus(400);
3execFile("ping", ["-c", "1", host], onResult);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

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References

github.com/NagiosEnterprises/nagioscore/blob/master/Changelog

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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