CVE-2026-48551 in Nagios Core
Summary
by MITRE • 08/12/2026
Nagios Core before 4.5.14 and Nagios XI before 2026R1.7 contain a cross-site request forgery protection bypass via a self-supplied double-submit cookie. An attacker can supply matching cookie and request parameter values to bypass CSRF protection, enabling unauthenticated attackers to run commands as authorized users via malicious links.
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Analysis
by VulDB Data Team • 08/12/2026
This vulnerability affects Nagios Core versions prior to 4.5.14 and Nagios XI versions prior to 2026R1.7, representing a critical cross-site request forgery flaw that undermines the security model of these network monitoring solutions. The vulnerability stems from an insufficient CSRF protection mechanism that relies on a double-submit cookie pattern but fails to properly validate the consistency between the cookie value and the request parameter, creating a bypass opportunity for attackers.
The technical implementation flaw occurs when the application accepts user-supplied values for both the cookie and corresponding request parameters without proper validation of their matching relationship. This allows an attacker to craft malicious links that include both matching cookie and parameter values, effectively circumventing the CSRF protection mechanism. The vulnerability is categorized under CWE-352 as a Cross-Site Request Forgery issue, where the protection mechanism fails to properly validate the authenticity of requests. The flaw enables attackers to execute arbitrary commands as authenticated users by leveraging the double-submit cookie pattern that should have prevented such unauthorized operations.
The operational impact of this vulnerability is severe as it allows unauthenticated attackers to perform privileged actions within the Nagios monitoring environment. Since Nagios systems typically manage critical infrastructure monitoring and alerting, successful exploitation could lead to complete compromise of the monitoring infrastructure, including unauthorized access to system configurations, ability to manipulate alerts and notifications, and potential lateral movement within the network. The attack requires minimal user interaction since the malicious links can be delivered via phishing emails or compromised websites, making it particularly dangerous in enterprise environments where administrators frequently interact with web-based monitoring interfaces.
The vulnerability aligns with ATT&CK technique T1566.002 for phishing attacks and T1059.001 for command execution through web interfaces. Organizations using these vulnerable versions should immediately apply the official patches released by Nagios, Inc. that address the double-submit cookie validation mechanism. Additional mitigations include implementing proper input validation on all CSRF tokens, enforcing strict session management policies, and deploying web application firewalls to detect and block malicious requests. Network segmentation and monitoring of administrative interfaces can also help detect anomalous command execution patterns that may indicate exploitation attempts. The fix typically involves strengthening the CSRF protection logic to ensure that cookie values and request parameters are consistently validated against each other rather than simply accepting matching user-supplied values as legitimate authentication.