CVE-2017-18240 in app-admin collectd
Summary
by MITRE
The Gentoo app-admin/collectd package before 5.7.2-r1 sets the ownership of PID file directory to the collectd account, which might allow local users to kill arbitrary processes by leveraging access to this account for PID file modification before a root script sends a SIGKILL (when the service is stopped).
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Analysis
by VulDB Data Team • 01/14/2020
The vulnerability identified as CVE-2017-18240 affects the Gentoo collectd package version 5.7.2-r1 and earlier, representing a critical privilege escalation issue within system service management. This flaw stems from improper handling of PID file directory ownership during the collectd service initialization process. The vulnerability creates a window of opportunity for local attackers who can leverage access to the collectd account to manipulate PID files and subsequently execute malicious process termination commands. The root cause lies in the package's failure to properly secure the directory containing the PID file, allowing unauthorized modification of process identifiers that should remain protected. This misconfiguration enables attackers to escalate privileges by targeting the service stopping mechanism and exploiting the timing gap between PID file modification and the root script execution that sends SIGKILL signals.
The technical exploitation of this vulnerability involves a race condition scenario where local users with access to the collectd account can modify PID files in the directory before the root script executes its cleanup routine. This race condition creates a temporal vulnerability window where the attacker can manipulate process identifiers to target arbitrary processes on the system. The flaw directly relates to CWE-362, which addresses concurrent execution issues leading to race conditions, and CWE-276, concerning improper file permissions that allow unauthorized access. When collectd starts, it creates PID files in a directory that it sets to be owned by the collectd user account, but fails to properly restrict write permissions for this directory. This design flaw allows attackers to modify the PID files, potentially causing the service stopping script to send termination signals to unintended processes, effectively enabling process injection or arbitrary process killing.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system stability and security integrity concerns. Attackers can leverage this vulnerability to disrupt critical services by targeting their PIDs, causing service outages or potentially creating denial of service conditions. The vulnerability also provides a pathway for attackers to gain deeper system access by manipulating the collectd service lifecycle, which could be particularly damaging in environments where collectd is used for monitoring and logging critical system functions. Security implications include the potential for attackers to target other services running under different user contexts, as the ability to manipulate process identifiers can be extended to compromise the broader system security posture. The vulnerability is particularly concerning in multi-tenant environments or systems where the collectd account has broader access rights than typical monitoring services would require.
Mitigation strategies for CVE-2017-18240 should prioritize immediate package updates to version 5.7.2-r1 or later, which contain the necessary fixes for proper PID file directory ownership handling. System administrators should implement additional controls such as restricting write permissions on PID file directories and ensuring that the collectd service runs with minimal necessary privileges. The implementation of proper access controls and monitoring of process identifier modifications can help detect exploitation attempts. Organizations should also consider implementing the principle of least privilege for the collectd account, limiting its access rights to only those necessary for its monitoring functions. Security teams should monitor for unusual process termination patterns that might indicate exploitation attempts, and consider implementing process integrity checks that can detect unauthorized PID file modifications. The fix addresses the underlying issue by ensuring that the PID file directory is properly secured with appropriate ownership and permissions, preventing local users from modifying the files that control service lifecycle management. This vulnerability highlights the importance of proper privilege separation and secure service initialization in maintaining system integrity and preventing local privilege escalation attacks.