CVE-2015-3940 in Wonderware System Platform
Summary
by MITRE
Untrusted search path vulnerability in Schneider Electric Wonderware System Platform before 2014 R2 Patch 01 allows local users to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 06/07/2022
The vulnerability identified as CVE-2015-3940 represents a critical untrusted search path issue within Schneider Electric Wonderware System Platform versions prior to 2014 R2 Patch 01. This flaw resides in the software's dynamic link library loading mechanism, where the application fails to properly validate the source and integrity of dynamically loaded modules. The vulnerability stems from the system's default behavior of searching for required DLL files in a predetermined set of directories, including the current working directory, without implementing proper security checks to ensure that these modules originate from trusted sources. This design flaw creates an opportunity for malicious actors to place specially crafted Trojan horse DLL files in strategic locations within the file system, thereby enabling privilege escalation attacks.
The technical exploitation of this vulnerability occurs through a well-known attack pattern that aligns with CWE-426 Untrusted Search Path, where an application searches for libraries in directories that are not properly secured or validated. When the Wonderware System Platform executes, it follows a predictable search order that includes the current working directory, which can be manipulated by local users. Attackers can leverage this by placing a malicious DLL with the same name as a legitimate system DLL in a directory that gets searched before the legitimate DLL location. This allows the system to load the attacker-controlled code instead of the intended legitimate module, effectively enabling code execution with the privileges of the running process. The vulnerability specifically impacts local users who have access to the system, as the attack requires the ability to write files to directories that will be searched by the application.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides a persistent foothold for attackers within the industrial control system environment. In industrial settings where Wonderware System Platform is deployed for process control and monitoring, this vulnerability can be leveraged to execute arbitrary code on critical infrastructure systems, potentially leading to disruption of operations, data manipulation, or even physical safety hazards. The vulnerability is particularly concerning in environments where multiple users have local access to the system, as it requires minimal privileges to exploit. The attack vector does not require network access or complex exploitation techniques, making it accessible to attackers with basic local system access. This characteristic makes the vulnerability especially dangerous in environments where security boundaries are not properly enforced at the local system level.
Mitigation strategies for CVE-2015-3940 should focus on both immediate patching and operational security improvements. The primary recommendation involves applying the official patch released by Schneider Electric for the 2014 R2 Patch 01 update, which addresses the underlying search path vulnerability by implementing proper DLL loading security measures. Organizations should also implement the principle of least privilege for local system access, ensuring that only authorized personnel have the ability to write files to system directories. Additional security controls include implementing file integrity monitoring solutions that can detect unauthorized DLL placements, configuring the Windows file system to restrict write access to critical directories, and conducting regular security assessments of system configurations. The mitigation approach should align with ATT&CK technique T1055 Process Injection, as the vulnerability enables similar attack patterns where malicious code is injected into legitimate processes. Network segmentation and application whitelisting solutions can provide additional defense-in-depth measures to prevent exploitation even if the primary vulnerability is not patched.