What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-09-08
• Weakness: CWE-78

Description

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.

Affected products

• Nagios Enterprises, LLC. Nagios Core: before 4.5.13 — fixed in 4.5.13
• Nagios Enterprises, LLC. Nagios XI: before 2026R1.5 — fixed in 2026R1.5

How to fix

Upgrade to a fixed version: Nagios Enterprises, LLC. Nagios Core 4.5.13; Nagios Enterprises, LLC. Nagios XI 2026R1.5. Check the vendor advisory for mitigations.

References

• https://github.com/NagiosEnterprises/nagioscore/blob/master/Changelog
• https://www.nagios.com/security-disclosures/nagios-core/
• https://www.vulncheck.com/advisories/nagios-core-xi-authenticated-rce-via-custom-variable-macro-injection

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