Nagios Log Server Under Threat: CVE-2025-34323 Allows Local Privilege Escalation

Overview

CVE-2025-34323 describes a critical local privilege escalation vulnerability affecting Nagios Log Server versions prior to 2026R1.0.1. This flaw allows a local attacker, who has gained access to the web server user account, to gain root privileges on the affected system. This is achieved through a combination of insecure sudo rules and permissive file system permissions.

Technical Details

The vulnerability stems from a dangerous interaction between sudo rules and file system permissions. The web server account in vulnerable Nagios Log Server installations is granted passwordless sudo access to specific maintenance scripts. Simultaneously, this web server account is a member of a group that has write access to the directory containing these same maintenance scripts. This creates a scenario ripe for exploitation.

A local attacker, operating under the web server user’s context, can exploit this by:

1. Replacing one of the permitted maintenance scripts with a malicious program (e.g., a reverse shell or code that adds a root user).
2. Executing the modified script using sudo. Because the sudo rule is configured without a password prompt for the web server user for these scripts, the malicious program executes with root privileges.

This allows the attacker to execute arbitrary code with root privileges, effectively compromising the entire system.

CVSS Analysis

Due to the nature of this vulnerability, while no official CVSS score has been assigned, it would likely receive a high or critical CVSS score. The attack vector is local (requiring an existing foothold on the system), but the impact is complete compromise of confidentiality, integrity, and availability, as the attacker gains full root access. A likely CVSS score would be in the range of 7.0 to 9.0, depending on the specific configuration and environmental factors.

Possible Impact

Successful exploitation of CVE-2025-34323 can lead to severe consequences, including:

• Full System Compromise: The attacker gains complete control over the Nagios Log Server, including access to all logs and system configurations.
• Data Breach: Sensitive log data could be accessed, exfiltrated, or modified.
• Denial of Service: The attacker could render the Nagios Log Server inoperable, disrupting critical monitoring functions.
• Lateral Movement: The compromised server could be used as a launchpad to attack other systems on the network.
• Compliance Violations: A data breach could lead to significant legal and financial penalties.

Mitigation and Patch Steps

The primary mitigation step is to upgrade Nagios Log Server to version 2026R1.0.1 or later. This version contains a fix that addresses the vulnerability by correcting the insecure sudo rules and file system permissions.

1. Upgrade Nagios Log Server: Immediately upgrade to version 2026R1.0.1 or a later version.
2. Review Sudo Rules: Even after upgrading, review all sudo rules to ensure they follow the principle of least privilege. Avoid granting passwordless sudo access unless absolutely necessary.
3. Restrict File System Permissions: Ensure that the web server user does not have write access to directories containing critical system scripts or executables.
4. Implement Monitoring: Implement monitoring to detect any suspicious activity, such as unauthorized modifications to system files or unexpected sudo usage.

References

• Nagios Log Server 2026R1.0.1 Changelog
• Nagios Security Information
• VulnCheck Advisory for CVE-2025-34323