CVE-2008-0595 in Inter-process Communication System
Summary
by MITRE
dbus-daemon in D-Bus before 1.0.3, and 1.1.x before 1.1.20, recognizes send_interface attributes in allow directives in the security policy only for fully qualified method calls, which allows local users to bypass intended access restrictions via a method call with a NULL interface.
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Analysis
by VulDB Data Team • 08/06/2019
The vulnerability described in CVE-2008-0595 affects the D-Bus message bus system, specifically the dbus-daemon component responsible for handling security policies and access controls. This issue exists in D-Bus versions prior to 1.0.3 and 1.1.x versions before 1.1.20, representing a significant security flaw that undermines the intended access control mechanisms. The vulnerability stems from an incomplete implementation of security policy enforcement where the daemon fails to properly evaluate send_interface attributes in allow directives when method calls lack interface information.
The technical flaw manifests in how the dbus-daemon processes security policy rules that contain allow directives with send_interface attributes. These attributes are designed to restrict access to specific interfaces within the D-Bus system, but the implementation contains a critical oversight. When method calls are made without specifying an interface name, the daemon should still enforce the security policy restrictions defined by the send_interface attribute. However, due to the bug, the daemon completely ignores these security constraints when processing such method calls, effectively allowing unauthorized access to protected resources.
Local users can exploit this vulnerability by crafting method calls that omit interface information, thereby bypassing the intended access restrictions that should have been enforced through the security policy. This creates a privilege escalation scenario where unauthorized users can gain access to system resources that should be restricted to specific interfaces or applications. The vulnerability essentially creates a backdoor in the access control system, allowing malicious local processes to circumvent the security policies that were put in place to protect sensitive system components.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally compromises the integrity of the D-Bus security model. This weakness can be leveraged to execute arbitrary code, access sensitive system information, or disrupt services that depend on proper D-Bus interface access controls. Attackers can exploit this flaw to gain elevated privileges or perform actions that should be restricted to authorized applications, potentially leading to complete system compromise. The vulnerability affects systems that rely on D-Bus for inter-process communication and security policy enforcement, making it particularly dangerous in environments where multiple applications interact through the message bus.
This vulnerability aligns with CWE-284, which addresses improper access control issues, and can be mapped to ATT&CK techniques involving privilege escalation and persistence through system services. Organizations should implement immediate mitigations including upgrading to D-Bus versions 1.0.3 or 1.1.20 and higher, reviewing existing security policies to ensure proper interface specification, and monitoring for unauthorized D-Bus activity. The fix implemented by the D-Bus developers involved correcting the policy evaluation logic to properly handle method calls without explicit interface information, ensuring that send_interface attributes are consistently enforced regardless of method call format. System administrators should also consider implementing additional monitoring and logging mechanisms to detect potential exploitation attempts and verify that security policies are functioning as intended.