CVE-2018-11551 in PBX
Summary
by MITRE
AXON PBX 2.02 contains a DLL hijacking vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code on a targeted system. The vulnerability exists because a DLL file is loaded by 'pbxsetup.exe' improperly.
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Analysis
by VulDB Data Team • 02/11/2020
The vulnerability identified as CVE-2018-11551 affects AXON PBX version 2.02 and represents a critical DLL hijacking flaw that enables remote code execution without authentication. This vulnerability stems from improper handling of dynamic link library loading within the pbxsetup.exe application, creating a pathway for malicious actors to compromise targeted systems. The flaw specifically manifests when the application attempts to load a DLL file, which can be manipulated by an attacker to execute arbitrary code with the privileges of the targeted system.
This vulnerability aligns with CWE-426, which describes the improper handling of dynamic link library loading, and represents a classic example of a DLL hijacking attack vector. The attack occurs because pbxsetup.exe does not properly validate or restrict the paths from which it loads DLL dependencies, allowing an attacker to place malicious DLL files in directories that are searched before legitimate system locations. This behavior creates a race condition where the application loads attacker-controlled code instead of the intended legitimate libraries, effectively bypassing normal security controls and system protections.
The operational impact of this vulnerability is severe as it enables unauthenticated remote code execution, meaning attackers can compromise systems without requiring valid credentials or prior access. The attack surface extends to any system running the vulnerable AXON PBX 2.02 software, making it particularly dangerous in enterprise environments where PBX systems are commonly deployed. Once successful, the attacker gains the ability to execute commands with the privileges of the running process, potentially leading to complete system compromise, data exfiltration, or further lateral movement within the network. The vulnerability affects both Windows desktop and server operating systems where the PBX software is installed.
Mitigation strategies should focus on immediate patching of the affected software to the latest version that addresses the DLL loading issue. Organizations should also implement proper DLL loading security measures such as setting appropriate PATH environment variables, using application whitelisting solutions, and employing security tools that monitor for suspicious DLL loading activities. The use of Microsoft's Application Control features and implementing the principle of least privilege can significantly reduce the attack surface. Additionally, network segmentation and monitoring for unusual outbound connections from PBX systems can help detect exploitation attempts. This vulnerability demonstrates the importance of secure coding practices and proper DLL loading mechanisms, aligning with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. Organizations should also consider implementing endpoint detection and response solutions to identify and block suspicious DLL loading patterns that could indicate exploitation attempts.