CVE-2026-48553 Nagios Enterprises, LLC. CVE debrief

Who should care

Defenders responsible for Nagios Core and XI deployments, especially those using custom variables in shell-executed commands, should assess exposure and prioritize remediation. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify and remediate this high-severity vulnerability.

Why it matters

CVE-2026-48553 is a high-severity vulnerability in Nagios Core and XI that allows authenticated remote code execution via custom-variable macro injection. Defenders should prioritize verification, remediation, and monitoring to prevent potential exploitation.

• Verification of custom variable usage and NRDP access controls
• Potential for authenticated remote code execution
• Need for timely updates to Nagios Core 4.5.13 or later and Nagios XI 2026R1.5 or later
• Monitoring for suspicious NRDP activity

Technical summary

CVE-2026-48553 is an authenticated remote code execution vulnerability in Nagios Core before 4.5.13 and Nagios XI before 2026R1.5. The vulnerability is caused by custom-variable macro injection through the Nagios Remote Data Processor (NRDP). An authenticated attacker with NRDP access can inject OS commands through the macro value when a custom variable defined on a host, service, or contact is referenced in a shell-executed command line.

Defensive priority

Defenders should prioritize verifying and remediating this vulnerability in Nagios Core and XI deployments, especially where custom variables are used in shell-executed commands.

Recommended defensive actions

• Verify Nagios Core and XI versions and configurations for potential exposure
• Review custom variable usage in shell-executed commands
• Implement NRDP access controls and monitoring
• Update to Nagios Core 4.5.13 or later and Nagios XI 2026R1.5 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and NVD entry provide details on the authenticated remote code execution vulnerability in Nagios Core before 4.5.13 and Nagios XI before 2026R1.5. The vulnerability is related to custom-variable macro injection through the Nagios Remote Data Processor (NRDP).

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.