CVE-2017-1000082 in systemd
Summary
by MITRE
systemd v233 and earlier fails to safely parse usernames starting with a numeric digit (e.g. "0day"), running the service in question with root privileges rather than the user intended.
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Analysis
by VulDB Data Team • 05/21/2025
The vulnerability identified as CVE-2017-1000082 represents a critical privilege escalation flaw within systemd versions 233 and earlier, specifically affecting the service management component of Linux systems. This issue stems from inadequate input validation during username parsing operations, creating a scenario where system services could be inadvertently executed with elevated privileges. The flaw manifests when systemd encounters usernames that begin with numeric digits, a common practice in system administration and automation scripts where numeric prefixes serve various purposes including service identification and ordering. The vulnerability directly impacts the core system integrity by allowing unauthorized privilege escalation, potentially enabling attackers to gain root access through malicious service configurations.
The technical implementation of this vulnerability resides in systemd's username parsing logic where the system fails to properly validate or sanitize user identifiers that commence with numeric characters. This parsing error occurs within the service execution context where systemd determines the appropriate user context for service execution. When a service is configured with a username starting with a digit, the parsing routine incorrectly interprets this input, leading to the service being executed with root privileges instead of the intended non-privileged user account. The flaw operates at the boundary between user input validation and privilege management, creating a path where malformed username inputs can bypass normal security controls. This behavior aligns with CWE-20, "Improper Input Validation," and CWE-78, "Improper Neutralization of Special Elements used in OS Command," as the system fails to properly validate the username format before executing privilege escalation operations.
The operational impact of CVE-2017-1000082 extends beyond simple privilege escalation to encompass broader system compromise capabilities. Attackers can exploit this vulnerability to execute arbitrary code with root privileges, potentially leading to complete system takeover. The vulnerability affects systems where systemd manages services with numeric usernames, which is common in enterprise environments where automated deployment scripts and service management frameworks often utilize numeric prefixes for organizational purposes. This flaw particularly impacts systems running systemd versions prior to 234, where the parsing logic was corrected to properly validate username formats. The vulnerability can be leveraged through various attack vectors including compromised service files, malicious configuration changes, or by exploiting other weaknesses that allow modification of service definitions. From an attack perspective, this vulnerability maps to ATT&CK technique T1068, "Exploitation for Privilege Escalation," and T1059, "Command and Scripting Interpreter," as it enables attackers to execute commands with elevated privileges.
Mitigation strategies for CVE-2017-1000082 focus on immediate system updates and operational hardening measures. The primary remediation involves upgrading systemd to version 234 or later where the username parsing logic has been corrected to properly validate numeric usernames. System administrators should conduct comprehensive inventory checks to identify all systems running vulnerable systemd versions and prioritize patching operations. Additionally, operational security measures include implementing strict service file validation procedures, monitoring for unusual service execution patterns, and ensuring proper user account management practices that avoid numeric prefixes in service configurations where possible. Organizations should also implement network segmentation and access controls to limit potential exploitation paths, while maintaining regular vulnerability assessments to identify similar parsing or validation issues within other system components. The vulnerability demonstrates the critical importance of input validation in system management tools and highlights the need for comprehensive security testing of core system components that handle user privilege operations.