CVE-2017-14102 in MIMEDefang
Summary
by MITRE
MIMEDefang 2.80 and earlier creates a PID file after dropping privileges to a non-root account, which might allow local users to kill arbitrary processes by leveraging access to this non-root account for PID file modification before a root script executes a "kill `cat /pathname`" command, as demonstrated by the init-script.in and mimedefang-init.in scripts.
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Analysis
by VulDB Data Team • 12/27/2022
The vulnerability described in CVE-2017-14102 affects MIMEDefang versions 2.80 and earlier, presenting a critical privilege escalation risk through improper PID file handling during service initialization. This flaw occurs when the MIMEDefang service creates a PID file while operating under non-root privileges, creating a window of opportunity for local attackers who have access to the non-root account to manipulate the PID file before the root script executes a kill command based on the file contents. The vulnerability specifically impacts the init-script.in and mimedefang-init.in scripts, which are responsible for managing the service lifecycle and contain the problematic code pattern that enables this attack vector.
The technical implementation of this vulnerability stems from a fundamental flaw in process management and privilege separation within the MIMEDefang initialization sequence. When the service starts, it drops privileges from root to a non-root user account to enhance security, but it still creates a PID file in a location where the non-root user has write permissions. This PID file contains the process identifier of the root-owned service, and when the root script executes a command such as "kill `cat /pathname`", it reads this file and attempts to terminate the process identified within it. However, since the non-root user can modify the PID file contents, they can manipulate the target process that the root script attempts to kill, effectively allowing them to target any process running on the system.
This vulnerability operates under the principles of privilege escalation and process manipulation, aligning with CWE-276, which addresses improper privileges, and CWE-78, which covers improper neutralization of special elements used in OS commands. The attack vector specifically relates to the ATT&CK technique T1068, which involves exploiting vulnerabilities in privilege escalation, and T1133, which encompasses persistence and privilege escalation through process injection or manipulation. The flaw demonstrates a classic race condition where the timing between process creation and privilege dropping creates an exploitable window for manipulation.
The operational impact of this vulnerability extends beyond simple process termination, as it provides attackers with a method to manipulate critical system processes and potentially escalate their privileges further. Local users with access to the non-root account can leverage this to kill system processes, including those critical for security monitoring, network services, or other essential system functions. The attack requires minimal privileges and can be executed without requiring additional system access, making it particularly dangerous in environments where multiple users share system resources or where accounts are compromised through other means. This vulnerability undermines the fundamental security principle of privilege separation and creates an attack surface that allows for arbitrary process manipulation through simple file modification.
Mitigation strategies for CVE-2017-14102 involve addressing the core issue of PID file creation and privilege management during service initialization. The most effective approach is to ensure that PID files are created with appropriate permissions and are not writable by non-root users, or alternatively, to implement proper privilege separation by creating PID files before dropping privileges. System administrators should upgrade to MIMEDefang version 2.81 or later, which contains the fix for this vulnerability. Additionally, implementing proper file system permissions and access controls, such as setting restrictive permissions on PID file locations and using immutable file attributes, can prevent unauthorized modifications. Network segmentation and privilege monitoring can also help detect and prevent exploitation attempts. The fix typically involves modifying the initialization scripts to ensure that PID files are created with appropriate ownership and permissions before the privilege dropping occurs, thereby eliminating the window of opportunity for attackers to manipulate the file contents.