CVE-2017-16933 in Icinga
Summary
by MITRE
etc/initsystem/prepare-dirs in Icinga 2.x through 2.8.0 has a chown call for a filename in a user-writable directory, which allows local users to gain privileges by leveraging access to the $ICINGA2_USER account for creation of a link.
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Analysis
by VulDB Data Team • 01/16/2023
The vulnerability identified as CVE-2017-16933 affects Icinga 2 versions 2.8.0 and earlier, specifically within the etc/initsystem/prepare-dirs component. This flaw represents a privilege escalation vulnerability that exploits a design weakness in how the system handles directory preparation during initialization. The vulnerability occurs when the prepare-dirs script executes a chown system call on a filename located within a directory that is writable by users, creating an opportunity for malicious actors to manipulate the system's permission structure.
The technical implementation of this vulnerability stems from improper privilege management during system initialization. When Icinga 2 executes the prepare-dirs script, it performs a chown operation on a file that exists in a user-writable directory. This creates a race condition scenario where a local user with access to the $ICINGA2_USER account can create symbolic links in the vulnerable directory. The attacker can then manipulate the chown operation to change ownership of files outside the intended scope, effectively allowing privilege escalation from the regular user account to the Icinga 2 service account or potentially higher privileges.
This vulnerability aligns with CWE-276, which describes improper file permissions, and CWE-269, which covers improper privilege management. The flaw enables local privilege escalation through a path traversal and symbolic link manipulation technique, allowing attackers to gain elevated system privileges. The attack vector requires the attacker to have access to the $ICINGA2_USER account, which is a common scenario in environments where Icinga 2 is installed with default configurations or where users have been granted access for legitimate administrative purposes.
The operational impact of this vulnerability is significant for organizations running affected Icinga 2 versions. A local attacker with access to the Icinga 2 user account can escalate privileges to gain system-level access, potentially allowing them to modify critical monitoring configurations, access sensitive data, or establish persistent access to the system. This vulnerability undermines the security model of Icinga 2 by allowing unauthorized privilege escalation through a legitimate system initialization process. The vulnerability also relates to ATT&CK technique T1068, which covers local privilege escalation, and T1543, which covers create or modify system process, as the attack leverages legitimate system processes to achieve unauthorized access.
Mitigation strategies for this vulnerability include upgrading to Icinga 2 version 2.8.1 or later, which contains the fix for this privilege escalation issue. Organizations should also implement proper file system permissions, ensuring that directories used during system initialization are not writable by non-privileged users. Additionally, system administrators should review and restrict access to the $ICINGA2_USER account to minimize the attack surface. The fix typically involves modifying the prepare-dirs script to use more secure file handling techniques that prevent symbolic link manipulation during chown operations. Security monitoring should also be enhanced to detect unusual file system changes or privilege escalation attempts in Icinga 2 related processes, as this vulnerability may be exploited as part of broader attack campaigns targeting system monitoring infrastructure.