CVE-2014-3639 in D-Bus
Summary
by MITRE
The dbus-daemon in D-Bus before 1.6.24 and 1.8.x before 1.8.8 does not properly close old connections, which allows local users to cause a denial of service (incomplete connection consumption and prevention of new connections) via a large number of incomplete connections.
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Analysis
by VulDB Data Team • 03/29/2022
The vulnerability identified as CVE-2014-3639 affects the D-Bus message bus system, specifically the dbus-daemon component that serves as the central communication hub for applications on Linux systems. This flaw exists in D-Bus versions prior to 1.6.24 and 1.8.8, representing a critical security issue that undermines the reliability and availability of system services. The D-Bus protocol is fundamental to desktop environments and system services on Linux platforms, enabling inter-process communication between applications and system components. When compromised, this vulnerability can severely impact system stability and operational continuity.
The technical root cause of this vulnerability lies in the improper handling of connection management within the dbus-daemon process. Specifically, the daemon fails to properly close old connections when they become inactive or incomplete, leading to a gradual accumulation of stale connection handles in memory. This behavior creates a resource leak scenario where the system's connection table fills up with abandoned connections that are not being properly cleaned up. The flaw manifests when local users can exploit this weakness by establishing a large number of incomplete connections to the D-Bus daemon, causing it to consume all available connection slots and preventing legitimate new connections from being established.
From an operational impact perspective, this vulnerability enables local users to execute a denial of service attack against the D-Bus system, effectively disrupting communication between applications and system services. The incomplete connection consumption prevents new legitimate connections from being accepted, creating a cascading failure that can affect desktop environments, system daemons, and application services that depend on D-Bus communication. This attack vector is particularly concerning because it requires minimal privileges and can be executed by any local user, making it a significant threat to system availability. The vulnerability aligns with CWE-400, which categorizes resource management flaws that can lead to denial of service conditions.
The attack pattern for this vulnerability follows the characteristics described in ATT&CK technique T1499, which involves creating a denial of service condition through resource exhaustion. Local attackers can leverage this weakness by programmatically establishing numerous incomplete connections to the D-Bus daemon, gradually consuming all available connection slots. The impact extends beyond simple service disruption, as many system components rely on D-Bus for critical operations such as session management, device monitoring, and system notifications. When the daemon becomes unable to accept new connections, users may experience complete system unresponsiveness or application failures.
Mitigation strategies for CVE-2014-3639 primarily involve updating to patched versions of D-Bus, specifically versions 1.6.24 or later for the 1.6.x branch and 1.8.8 or later for the 1.8.x branch. System administrators should prioritize patching this vulnerability across all affected systems, particularly those running desktop environments or services that heavily depend on D-Bus communication. Additional protective measures include implementing connection limits and monitoring for unusual connection patterns, though these are secondary to the primary remediation of updating the software. The vulnerability demonstrates the importance of proper resource management in system services and highlights the need for robust connection handling mechanisms to prevent resource exhaustion attacks. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and prevent exploitation of similar vulnerabilities in the future.