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

> Authenticated attackers can execute arbitrary OS commands via macro injection in custom variables if referenced in shell commands.

- **Severity:** High 7.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-48553, GHSA-r6wg-9vj9-rm67, UBUNTU-CVE-2026-48553

## What is CVE-2026-48553?

CVE-2026-48553 is a high-severity command injection vulnerability in Nagios Core, published on 12 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-48553?


## How do I fix CVE-2026-48553?

Upgrade to a fixed version.

## Is CVE-2026-48553 being exploited?

There is no known exploitation of CVE-2026-48553 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48553 and fix it if it is affected.

What it is: CVE-2026-48553 is a high-severity command injection vulnerability in Nagios Core, published on 12 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-48553 in the wild and no public exploit code.

Affected product: Nagios Core. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48553/ (Markdown: https://insights.sbomify.com/CVE-2026-48553/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48553
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48553
- OSV: https://osv.dev/vulnerability/CVE-2026-48553

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48553/
Summaries are generated and may contain mistakes; the official description above is the record.