CVE-2016-4349 in WebEx Productivity Tools
Summary
by MITRE
Untrusted search path vulnerability in Cisco WebEx Productivity Tools 2.40.5001.10012 allows local users to gain privileges via a Trojan horse cryptsp.dll, dwmapi.dll, msimg32.dll, ntmarta.dll, propsys.dll, riched20.dll, rpcrtremote.dll, secur32.dll, sxs.dll, or uxtheme.dll file in the current working directory, aka Bug ID CSCuy56140.
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Analysis
by VulDB Data Team • 11/02/2018
This vulnerability represents a classic untrusted search path issue affecting Cisco WebEx Productivity Tools version 2.40.5001.10012, which falls under the Common Weakness Enumeration category CWE-427. The flaw arises from the application's failure to properly validate the source of dynamic link library files during the loading process, creating a privilege escalation vector that can be exploited through a Trojan horse attack. When the application executes, it searches for specific system libraries in the current working directory before checking the standard system paths, allowing an attacker to place malicious versions of these DLL files in the same directory as the vulnerable application.
The affected DLL files include cryptsp.dll, dwmapi.dll, msimg32.dll, ntmarta.dll, propsys.dll, riched20.dll, rpcrtremote.dll, secur32.dll, sxs.dll, and uxtheme.dll, all of which are legitimate Windows system components that the application may load during normal operation. This vulnerability maps to the ATT&CK technique T1068 which focuses on exploiting local privilege escalation opportunities. Attackers can leverage this weakness by placing malicious DLL files with the same names as the legitimate system DLLs in the directory where WebEx Productivity Tools is executed, causing the application to load the attacker-controlled code instead of the genuine system libraries.
The operational impact of this vulnerability is significant as it allows local users to execute arbitrary code with the privileges of the target user, potentially enabling full system compromise if the user has elevated permissions. The attack requires local access and minimal privileges to execute, making it particularly dangerous in environments where users may have access to the application directory. The vulnerability demonstrates a fundamental flaw in the application's security design where it does not implement proper DLL loading security measures such as specifying full paths or using SafeDllSearchMode. This weakness can be exploited in various attack scenarios including social engineering campaigns where users might be tricked into executing malicious code or through compromised user accounts that gain access to the application's execution environment.
The vulnerability can be mitigated through several approaches including updating to a patched version of Cisco WebEx Productivity Tools, implementing proper DLL loading security practices, and using security software that monitors for suspicious DLL loading behavior. Organizations should also consider implementing the principle of least privilege and restricting local file system access to application directories. The ATT&CK framework suggests monitoring for unusual DLL loading patterns and implementing application whitelisting to prevent execution of unauthorized DLL files. Additionally, system administrators should ensure that the Windows SafeDllSearchMode registry setting is properly configured to prioritize system directories over the current working directory when loading DLLs, thereby preventing this type of attack vector from succeeding.