CVE-2017-14730 in logstash-bin
Summary
by MITRE
The init script in the Gentoo app-admin/logstash-bin package before 5.5.3 and 5.6.x before 5.6.1 has "chown -R" calls for user-writable directory trees, which allows local users to gain privileges by leveraging access to a $LS_USER account for creation of a hard link.
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Analysis
by VulDB Data Team • 12/30/2022
The vulnerability identified as CVE-2017-14730 affects the Gentoo package management system through the logstash-bin application, specifically targeting versions prior to 5.5.3 and 5.6.x before 5.6.1. This issue manifests within the init script component that governs the application's startup and initialization process, creating a critical privilege escalation vector. The flaw exploits a fundamental weakness in how file ownership permissions are handled during the application's initialization sequence, particularly when processing user-writable directory structures. The vulnerability arises from the use of chown -R commands that recursively change ownership of directory trees, creating an exploitable race condition that adversaries can leverage to elevate their system privileges.
The technical implementation of this vulnerability stems from improper handling of file system permissions during the logstash application initialization process. When the init script executes chown -R commands on directory trees that are writable by the $LS_USER account, it creates a window of opportunity for local attackers to manipulate the file system. The vulnerability specifically exploits the ability of an attacker with access to the $LS_USER account to create hard links to files within these directory structures. This race condition occurs because the chown command operates on directory trees that may contain symbolic links or hard links, allowing an attacker to manipulate the ownership of files in unexpected ways. The flaw is classified as a privilege escalation vulnerability under CWE-264, which specifically addresses permissions, privileges, and access controls. The attack vector involves the attacker creating a hard link to a file that will later be processed by the chown -R command, effectively allowing them to change the ownership of arbitrary files on the system.
The operational impact of CVE-2017-14730 extends beyond simple privilege escalation to encompass broader system compromise possibilities. An attacker who successfully exploits this vulnerability can gain elevated privileges that enable them to modify critical system files, install malicious software, or establish persistent access to the compromised system. The vulnerability affects systems where logstash is deployed with user accounts that have write access to directory trees that are later processed by chown -R commands during initialization. This creates a persistent threat vector that remains active until the system is updated with the patched version of the logstash-bin package. The vulnerability's exploitation aligns with techniques described in the MITRE ATT&CK framework under privilege escalation tactics, specifically targeting the use of insecure file permissions and race conditions as attack vectors. Systems running vulnerable versions of the Gentoo logstash-bin package are particularly at risk because the init script executes with elevated privileges, making the potential impact of successful exploitation significantly more severe.
Mitigation strategies for CVE-2017-14730 require immediate patching of the affected Gentoo package to version 5.5.3 or later 5.6.x releases that contain the necessary fixes. Organizations should also implement additional security controls including restricting write access to directory trees that are processed by chown -R commands, implementing proper file system permission controls, and conducting regular audits of init scripts and privilege escalation mechanisms. System administrators should review and tighten the permissions of user accounts that have access to the $LS_USER account to minimize the attack surface. The fix typically involves modifying the init script to avoid recursive ownership changes on potentially writable directory trees or implementing proper synchronization mechanisms to prevent race conditions. Additionally, monitoring systems should be configured to detect unusual chown operations or privilege escalation attempts that might indicate exploitation attempts. Security teams should also consider implementing principle of least privilege practices for logstash user accounts and ensure that all system components are regularly updated to address known vulnerabilities. The vulnerability demonstrates the importance of secure coding practices in system initialization scripts and highlights the need for careful permission management in multi-user environments where privilege escalation vectors can be exploited through seemingly benign operations.