CVE-2014-3635 in D-Bus
Summary
by MITRE
Off-by-one error in D-Bus 1.3.0 through 1.6.x before 1.6.24 and 1.8.x before 1.8.8, when running on a 64-bit system and the max_message_unix_fds limit is set to an odd number, allows local users to cause a denial of service (dbus-daemon crash) or possibly execute arbitrary code by sending one more file descriptor than the limit, which triggers a heap-based buffer overflow or an assertion failure.
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Analysis
by VulDB Data Team • 03/29/2022
The vulnerability identified as CVE-2014-3635 represents a critical off-by-one error within the D-Bus message bus system affecting versions 1.3.0 through 1.6.x before 1.6.24 and 1.8.x before 1.8.8. This flaw specifically manifests on 64-bit systems when the max_message_unix_fds configuration parameter is set to an odd numerical value, creating a dangerous condition that can be exploited by local attackers to compromise system stability and potentially execute arbitrary code. The issue stems from improper boundary checking in the D-Bus daemon's handling of Unix file descriptors, where the system fails to properly validate the number of file descriptors being processed against the configured limit.
The technical exploitation of this vulnerability occurs through a heap-based buffer overflow condition that arises when an attacker sends one additional file descriptor beyond the configured limit. This seemingly minor deviation from the expected parameter causes the D-Bus daemon to miscalculate memory allocation and buffer boundaries, leading to memory corruption that can result in either a crash of the dbus-daemon process or more severe consequences including arbitrary code execution. The flaw is classified as a CWE-129 Input Validation and the vulnerability type aligns with ATT&CK technique T1059.007 for command and script injection, as successful exploitation could enable attackers to execute malicious code within the context of the D-Bus service. The heap-based overflow specifically relates to CWE-122, which deals with heap-based buffer overflow conditions, making this vulnerability particularly dangerous in environments where D-Bus is used for inter-process communication.
The operational impact of CVE-2014-3635 extends beyond simple denial of service scenarios, as the potential for arbitrary code execution creates a significant security risk for systems relying on D-Bus for critical communication pathways. Local users with access to the system can leverage this vulnerability to disrupt services, potentially gaining elevated privileges or compromising the integrity of applications that depend on D-Bus for their operation. The vulnerability affects systems where D-Bus is actively running and processing file descriptor communications, making it particularly relevant in desktop environments, server configurations, and embedded systems that utilize D-Bus for service communication. The specific trigger condition of odd-numbered max_message_unix_fds limits means that administrators must be particularly vigilant when configuring D-Bus parameters, as even seemingly benign configuration changes can introduce security risks.
Mitigation strategies for this vulnerability include immediate patching of D-Bus installations to versions 1.6.24 or 1.8.8 and later, which contain the necessary fixes to address the boundary checking error. System administrators should also consider implementing monitoring for unusual file descriptor usage patterns and reviewing D-Bus configuration parameters to avoid setting max_message_unix_fds to odd values when possible. The fix addresses the underlying buffer overflow condition by implementing proper boundary validation and ensuring that memory allocation matches the actual number of file descriptors being processed. Additionally, organizations should conduct vulnerability assessments to identify systems running affected D-Bus versions and implement configuration management practices that prevent the problematic parameter settings from being applied in production environments. This vulnerability demonstrates the importance of thorough input validation in system-level software components and highlights how seemingly minor implementation flaws can have significant security implications in communication frameworks that are fundamental to modern operating systems.