CVE-2015-2285 in Upstart
Summary
by MITRE
The logrotation script (/etc/cron.daily/upstart) in the Ubuntu Upstart package before 1.13.2-0ubuntu9, as used in Ubuntu Vivid 15.04, allows local users to execute arbitrary commands and gain privileges via a crafted file in /run/user/*/upstart/sessions/.
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Analysis
by VulDB Data Team • 11/27/2024
The vulnerability CVE-2015-2285 represents a critical privilege escalation flaw in the Ubuntu Upstart package that affects systems running Ubuntu Vivid 15.04 and earlier versions. This issue resides within the logrotation script located at /etc/cron.daily/upstart, which is designed to manage system logging processes but contains a dangerous flaw that allows local attackers to execute arbitrary code with elevated privileges. The vulnerability specifically targets the upstart session management system and leverages improper file handling within the /run/user/*/upstart/sessions/ directory structure, creating a path traversal and command execution vector that bypasses normal security controls.
The technical implementation of this vulnerability stems from insufficient input validation and improper privilege handling within the upstart logrotation script. When the script processes session files in the /run/user/*/upstart/sessions/ directory, it fails to properly sanitize or validate the contents of these files before executing any commands they might contain. This design flaw allows malicious users to craft specially formatted files within the session directory that, when processed by the cron job, result in arbitrary command execution. The vulnerability operates under CWE-22 Path Traversal and CWE-78 Improper Neutralization of Special Elements used in OS Commands, both of which are well-documented weakness categories in the Common Weakness Enumeration framework. The flaw essentially allows attackers to inject malicious commands into the system through legitimate session management processes.
The operational impact of CVE-2015-2285 is severe and far-reaching, as it provides local users with a straightforward path to privilege escalation from regular user accounts to root privileges. Attackers can exploit this vulnerability by placing malicious files in the designated session directory, which are then executed by the upstart logrotation script during its daily cron execution. This creates a persistent backdoor mechanism that can be used to establish long-term system compromise, allowing adversaries to gain full administrative control over affected systems. The vulnerability is particularly dangerous because it operates silently in the background, leveraging legitimate system processes to execute malicious code without raising immediate suspicion, aligning with ATT&CK technique T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation.
Mitigation strategies for CVE-2015-2285 require immediate system updates to the patched version of the Ubuntu Upstart package, specifically version 1.13.2-0ubuntu9 or later, which addresses the improper file handling and privilege escalation paths. System administrators should also implement additional security controls such as restricting write access to the /run/user/*/upstart/sessions/ directory and monitoring for unauthorized file modifications in these locations. The fix involves proper input validation and sanitization of session files, ensuring that any commands executed are properly escaped and validated before processing. Organizations should also conduct thorough security audits to verify that no malicious files exist in the affected directory structures and implement proper access controls to prevent unauthorized users from creating or modifying files in privileged system directories. This vulnerability highlights the importance of proper privilege separation and input validation in system management scripts, particularly those that execute with elevated privileges as part of automated cron jobs.