CVE-2016-9566 in Nagios
Summary
by MITRE
base/logging.c in Nagios Core before 4.2.4 allows local users with access to an account in the nagios group to gain root privileges via a symlink attack on the log file. NOTE: this can be leveraged by remote attackers using CVE-2016-9565.
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Analysis
by VulDB Data Team • 11/29/2024
The vulnerability described in CVE-2016-9566 represents a critical privilege escalation flaw within Nagios Core versions prior to 4.2.4. This issue resides in the base/logging.c component of the monitoring software, which is widely deployed across enterprise environments for system and network monitoring. The vulnerability specifically affects systems where local users possess membership in the nagios group, creating a dangerous attack surface that can be exploited to achieve root-level privileges.
The technical exploitation mechanism involves a carefully crafted symlink attack against the log file handling process. When Nagios Core operates with elevated privileges to write log files, local users who are part of the nagios group can manipulate symbolic links to redirect logging operations to arbitrary files. This allows attackers to write content to locations they would normally not have access to, potentially enabling them to overwrite critical system files or inject malicious code into the logging infrastructure. The flaw stems from insufficient validation of symbolic link targets during the logging process, creating a path traversal vulnerability that can be leveraged for privilege escalation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can be combined with other exploits to create more sophisticated attack vectors. The description notes that this vulnerability can be leveraged by remote attackers using CVE-2016-9565, indicating a chained attack scenario where initial remote access is achieved through a different vulnerability, followed by local privilege escalation using CVE-2016-9566. This combination creates a particularly dangerous threat model where attackers can move from remote command execution to full system compromise without requiring additional access mechanisms.
From a cybersecurity perspective, this vulnerability aligns with CWE-59: Improper Link Resolution, which specifically addresses issues related to symbolic link manipulation in security contexts. The attack pattern follows elements of the ATT&CK framework's privilege escalation techniques, particularly those involving exploitation of system-level processes and file permissions. Organizations running Nagios Core versions prior to 4.2.4 face significant risk exposure, as this vulnerability can be exploited by attackers with minimal privileges to gain complete control over affected systems. The impact is particularly severe in environments where Nagios runs with elevated privileges and where multiple users have access to the nagios group membership, creating widespread potential compromise scenarios.
The recommended mitigations include immediate upgrade to Nagios Core version 4.2.4 or later, which contains the necessary patches to address the symbolic link handling issue. Additionally, system administrators should implement strict file permissions and access controls to minimize the potential impact of such vulnerabilities. Regular security auditing of monitoring infrastructure and proper privilege separation practices should be enforced to reduce the attack surface. The vulnerability demonstrates the critical importance of validating file operations and symbolic link resolution in security-sensitive applications, particularly those that operate with elevated privileges. Organizations should also consider implementing monitoring solutions that can detect anomalous file system activities related to log file manipulation, as this type of attack may not be immediately obvious through standard security controls.