CVE-2026-119742
Received Received - Intake

OS Command Injection in Nagios XI Prior to 2026R2

Publication date: 2026-11-03

Last updated on: 2026-11-03

Assigner: VulnCheck

Description
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-substitution filter that omits semicolons, pipes, and non-space IFS whitespace characters before passing them to a grep command run 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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Meta Information

Published
2026-11-03
Last Modified
2026-11-03
Generated
2026-11-03
AI Q&A
2026-11-03
EPSS Evaluated
N/A
NVD
CVE-2026-119742
EUVD
EUVD-2026-115824

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
Nagios Enterprises, LLC Nagios XI 0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-78 The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

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Executive Summary

Nagios XI before 2026R2 has an OS command injection flaw in the MIB upload feature. The install_mib() function in mibs.php uses an incomplete character deny-list that misses semicolons and pipes, allowing attackers to bypass restrictions. An authenticated admin can upload a malicious MIB file with a crafted filename containing tab characters, then use a multipart POST request to pipe commands to sh via mibs.php, executing arbitrary OS commands as the web server user.

Detection Guidance

Check Nagios XI version with: grep -r 'define(' /usr/local/nagiosxi/var/ | grep 'version' | head -1. If version is before 2026R2, the system is vulnerable. Inspect mibs.php for the install_mib() function to confirm the presence of the flawed filename sanitization logic.

Impact Analysis

This vulnerability allows authenticated administrators to execute arbitrary OS commands on the server running Nagios XI. An attacker could gain full control over the system, steal data, install malware, or disrupt services. The impact depends on the privileges of the web server user, which could be significant if the server has access to sensitive systems or data.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating compliance requirements under GDPR, HIPAA, and other regulations. Organizations using affected Nagios XI versions may face legal penalties, data breach notifications, and reputational damage if exploited. Immediate patching and security audits are recommended to maintain compliance.

Mitigation Strategies

Upgrade Nagios XI to version 2026R2 or later immediately. Temporarily restrict access to the mibs.php endpoint via web server rules until the upgrade is complete. Review and remove any unauthorized MIB files uploaded to the system.

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