CVE-2026-48548 in Nagios Core
Summary
by MITRE • 08/26/2026
Nagios Core before 4.5.12 contains a cross-site request forgery vulnerability in cmd.cgi where the CSRF protection mechanism passes validation when the NagFormId cookie is absent. Attackers can craft a malicious cross-site POST request to execute arbitrary Nagios commands as a currently authenticated user without their knowledge or consent.
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Analysis
by VulDB Data Team • 08/26/2026
The identified vulnerability resides within the command interface of Nagios Core, specifically affecting versions prior to 4.5.12. This security flaw is classified as a Cross-Site Request Forgery, which corresponds to CWE-352 in standard vulnerability taxonomy. The core issue stems from an insufficient validation mechanism within the cmd.cgi component, which serves as the primary interface for executing administrative commands through the Nagios web frontend. In a properly secured implementation, CSRF protections typically rely on verifying that incoming requests originate from legitimate pages served by the application itself, often using tokens or strict cookie checks to ensure user intent. However, in this specific version of Nagios Core, the validation logic is flawed because it considers the request valid if the NagFormId cookie is absent, rather than requiring its presence and validity. This logical inversion creates a significant security gap that allows unauthenticated attackers to bypass intended access controls when interacting with authenticated users.
The operational impact of this vulnerability is severe due to the nature of the commands executable through cmd.cgi. Since an attacker can craft malicious cross-site POST requests, they can trick an administrator who has already logged into the Nagios web interface into executing arbitrary system-level commands without their knowledge or consent. This capability aligns with several techniques in the MITRE ATT&CK framework, particularly T1078 Valid Accounts and T1203 Exploitation for Client Execution. By leveraging a victim's active session, an attacker can potentially disable monitoring services, alter configuration files, execute shell commands on the underlying operating system via CGI scripts, or disrupt critical infrastructure monitoring. The lack of user consent means that standard security awareness training is ineffective against this specific attack vector, as the actions appear to be initiated by the legitimate administrator from their own browser session.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary and most effective solution is to upgrade Nagios Core to version 4.5.12 or later, where the CSRF protection mechanism has been corrected to properly validate the presence and integrity of required cookies or tokens before processing any command requests. For environments where an immediate upgrade is not feasible due to compatibility constraints, temporary mitigations should be implemented at the network perimeter level. Web Application Firewalls can be configured to inspect outgoing POST requests from Nagios servers for missing or malformed CSRF tokens associated with cmd.cgi endpoints and block them accordingly. Additionally, restricting access to the Nagios web interface by IP address using firewall rules or reverse proxy configurations limits the attack surface by ensuring that only trusted internal networks can interact with the administrative console. Enabling strict SameSite cookie attributes on all session cookies further reduces the risk of cross-site request forgery by preventing browsers from sending these cookies in cross-origin requests, thereby neutralizing the exploitation vector described in this vulnerability analysis.