CVE-2017-7560 in rhnsd
Summary
by MITRE
It was found that rhnsd PID files are created as world-writable that allows local attackers to fill the disks or to kill selected processes.
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Analysis
by VulDB Data Team • 11/15/2019
The vulnerability identified as CVE-2017-7560 affects the rhnsd daemon component within Red Hat Network (RHN) systems, specifically targeting the improper permission handling of PID files. This flaw exists within the system management and monitoring infrastructure that facilitates communication between client systems and Red Hat Network servers. The rhnsd daemon is responsible for maintaining continuous communication with the RHN satellite server, enabling automated system updates, configuration management, and monitoring capabilities. When the daemon creates PID files during its operation, it establishes these files with world-writable permissions, creating a fundamental security weakness that undermines the integrity of the system's process management mechanisms.
The technical root cause of this vulnerability stems from the improper implementation of file permission controls within the rhnsd daemon's file creation routines. PID files serve as standard Unix/Linux system mechanisms for storing process identifiers, allowing other processes to interact with or control specific running applications. In this case, the daemon creates these files without setting appropriate restrictive permissions, allowing any local user on the system to modify or delete the PID file contents. This misconfiguration creates a privilege escalation vector where local attackers can manipulate the process management system to achieve unauthorized actions. The vulnerability manifests when the daemon writes its process identifier to a file that lacks proper access controls, specifically failing to set permissions such as 0600 or 0644 with appropriate ownership restrictions.
The operational impact of this vulnerability extends beyond simple disk filling attacks to encompass more sophisticated process manipulation capabilities that can disrupt system stability and availability. Local attackers with access to the compromised system can exploit this weakness by writing malicious process identifiers to the PID file, potentially causing the rhnsd daemon to target and terminate legitimate processes. This capability enables attackers to perform service disruption attacks that can compromise the integrity of system management functions, potentially leading to complete system availability loss. The vulnerability also facilitates disk space exhaustion attacks where malicious actors can continuously write to the PID file, filling available disk space and causing system instability. From an operational security perspective, this flaw undermines the trust model of the system's process management infrastructure, creating opportunities for attackers to escalate privileges or perform denial-of-service attacks against critical system management functions.
The vulnerability aligns with CWE-732, which addresses improper permission assignment, and represents a classic example of inadequate file permission management in system-level processes. From the ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and denial-of-service attack patterns, specifically targeting the system's process management and file system integrity. The attack surface is particularly concerning as it requires no special privileges beyond local system access, making it an attractive target for attackers who have already gained initial access to a system. Security professionals should note that this vulnerability affects systems where the rhnsd daemon is actively running and managing Red Hat Network connections, particularly in enterprise environments where automated system management is prevalent.
Mitigation strategies should focus on immediate permission corrections for existing PID files and implementation of proper file access controls within the daemon's codebase. System administrators should verify that all PID files created by rhnsd are set with restrictive permissions, typically 0600 or 0644, ensuring that only the owning process and authorized system administrators can modify these files. The most effective long-term solution involves patching the rhnsd daemon to implement proper file permission handling during PID file creation, ensuring that these files cannot be modified by unauthorized local users. Organizations should also implement monitoring systems to detect unauthorized modifications to critical system PID files and establish regular security audits to verify proper file permission settings. Additionally, system hardening measures should include ensuring that the rhnsd daemon runs with minimal required privileges and that unnecessary file system access permissions are removed to limit potential exploitation vectors.