CVE-2017-8934 in PCManFM
Summary
by MITRE
PCManFM 1.2.5 insecurely uses /tmp for a socket file, allowing a local user to cause a denial of service (application unavailability).
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-8934 affects PCManFM version 1.2.5, a popular file manager for the LXDE desktop environment. This issue represents a critical security flaw in how the application manages temporary files and inter-process communication mechanisms. The vulnerability stems from the application's insecure handling of socket file creation within the /tmp directory, which is a well-known security concern in Unix-like operating systems where /tmp is typically world-writable and accessible to all users on the system. This insecure practice creates a predictable attack surface that malicious local users can exploit to disrupt the normal operation of the file manager.
The technical flaw manifests when PCManFM creates a socket file in the /tmp directory during its operation, specifically during the initialization phase of the application. This socket file serves as a communication endpoint between different instances of the application or between the file manager and other system components. The vulnerability occurs because the application does not implement proper security measures such as creating the socket file with restricted permissions or using a more secure temporary directory. The use of /tmp for socket file creation violates fundamental security principles and creates a race condition vulnerability where an attacker can create a malicious socket file with the same name before the legitimate application instance can create it. This allows the attacker to either intercept communications or prevent the legitimate application from functioning properly.
The operational impact of this vulnerability extends beyond simple denial of service, as it fundamentally compromises the availability and integrity of the file management functionality within the LXDE desktop environment. When exploited, the vulnerability can cause PCManFM to crash or become unresponsive, rendering the file manager application unavailable to legitimate users. This disruption can occur at any time during normal operation, making it particularly dangerous in environments where users rely heavily on graphical file management tools. The attack vector is straightforward and requires only local system access, making it an attractive target for malicious actors who have already gained access to a system. This vulnerability can be particularly problematic in multi-user environments where one user might intentionally or unintentionally disrupt another user's file management capabilities. The impact is especially severe in automated or server environments where file manager availability is critical for system administration tasks.
Mitigation strategies for CVE-2017-8934 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves updating to a patched version of PCManFM that properly handles socket file creation using secure temporary directories with appropriate permissions. System administrators should also implement proper file system permissions and monitoring to detect unauthorized socket file creation attempts. The vulnerability aligns with CWE-377, which addresses insecure temporary file handling, and CWE-276, which covers improper file permissions. From an attack perspective, this vulnerability maps to ATT&CK technique T1489, which involves denying access to resources through various means including application-level denial of service. Organizations should also consider implementing additional security controls such as mandatory access controls, file integrity monitoring, and regular security audits to prevent similar issues in other applications. The fix should ensure that socket files are created in directories with restricted permissions and that proper atomic file creation operations are used to prevent race conditions. Additionally, system hardening measures such as disabling world-writable directories and implementing proper user isolation should be considered as part of a comprehensive security strategy.