---
id: "CVE-2026-119742"
kind: "vulnerability"
aliases: ["CVE-2026-119742"]
title: "Nagios XI: admin MIB upload lets a crafted filename run OS commands"
severity: "high"
cvss: 8.6
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "monitoring", "nagios-xi", "php", "self-hosted"]
not_affected_if: ["2026r2-or-later", "no-admin-exposure", "not-nagios-xi"]
published_at: "2026-11-03T14:17:34+00:00"
first_seen_at: "2026-11-03T14:21:08+00:00"
updated_at: "2026-11-03T14:22:01+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119742", "first_seen_at": "2026-11-03T14:21:08+00:00"}]
---

# Nagios XI: admin MIB upload lets a crafted filename run OS commands

Nagios XI before 2026R2 passes uploaded MIB filenames to a shell command using an incomplete character filter that misses semicolons and pipes. An attacker with administrator access can upload a file with a crafted name and run arbitrary commands as the web server user.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Nagios XI version in the web UI or on the server with the product's version file, and compare it to `2026R2`.
- Confirm whether the MIB upload feature is reachable by administrator accounts on the instance.

## Fix

- Nagios XI: upgrade to `2026R2` or later.

## Timeline

- 2026-11-03T14:21:08+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119742

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/nagios-xi-2026r2-os-command-injection-via-mibs-php

## From the sources

Nagios XI before 2026R2 contains an OS command injection vulnerability in the MIB upload feature where the install_mib() function in mibs.php sanitizes uploaded filenames with an incomplete character deny-list that omits semicolons and pipes before passing them to a grep command executed via exec(). An authenticated administrator can upload a MIB file with a crafted filename using tab characters to bypass the deny-list and pipe to sh via a multipart POST request to mibs.php, resulting in arbitrary OS command execution as the web server user.

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