CVE-2018-7799 in Software Update
Summary
by MITRE
A DLL hijacking vulnerability exists in Schneider Electric Software Update (SESU), all versions prior to V2.2.0, which could allow an attacker to execute arbitrary code on the targeted system when placing a specific DLL file.
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Analysis
by VulDB Data Team • 04/09/2020
The vulnerability identified as CVE-2018-7799 represents a critical DLL hijacking flaw within Schneider Electric Software Update (SESU) versions prior to V2.2.0, constituting a significant security risk for affected systems. This vulnerability stems from improper handling of dynamic link library loading mechanisms within the software update process, creating an exploitable condition that adversaries can leverage for privilege escalation and system compromise. The flaw specifically manifests when the vulnerable software attempts to load DLL files without proper validation of their source or location, allowing malicious actors to place crafted malicious DLLs in strategic directories where the update utility will subsequently load them. This type of vulnerability aligns with CWE-426, which addresses the dangerous use of external input in executing commands, and represents a classic example of insecure library loading practices that have been documented across numerous software platforms. The attack vector is particularly concerning because it requires minimal user interaction beyond the initial placement of the malicious DLL file, making it an attractive target for both automated and targeted attacks.
The technical implementation of this vulnerability involves the software update utility's failure to properly secure the dynamic link library loading sequence, which typically occurs during the software installation or update process. When SESU executes and attempts to load required libraries, it searches through a predefined set of directories in a specific order without validating whether the DLLs originate from trusted sources. This behavior creates a window of opportunity for attackers to place malicious DLLs in directories that are searched before legitimate system directories, effectively hijacking the execution flow. The vulnerability is particularly dangerous because it operates at the privilege level of the user running the update utility, which may be elevated if the software requires administrative permissions. This aspect of the vulnerability ties into ATT&CK technique T1059.001, which covers command and scripting interpreter usage, as the malicious code execution occurs through legitimate system mechanisms that are not properly secured against manipulation. The impact is further amplified by the fact that many organizations rely on automated update processes, making the exploitation of this vulnerability potentially widespread and difficult to detect.
The operational impact of CVE-2018-7799 extends beyond simple code execution, as it can enable attackers to establish persistent access to compromised systems and potentially escalate privileges to administrative levels. Once a malicious DLL is successfully loaded, attackers can execute arbitrary code with the privileges of the user running the SESU process, which may include system-level access. This capability allows for data exfiltration, system reconnaissance, and the installation of additional malicious software such as backdoors or rootkits. The vulnerability particularly affects industrial control systems and SCADA environments where Schneider Electric software is commonly deployed, making it a significant concern for critical infrastructure protection. Organizations using affected versions of SESU may find their systems vulnerable to supply chain attacks, where malicious actors compromise legitimate update channels to deliver malicious DLLs. The lack of proper DLL validation mechanisms means that even legitimate updates could be compromised if attackers can manipulate the update process. This vulnerability demonstrates the importance of proper software security practices and the need for robust library loading security measures. The exploitability of this vulnerability is further enhanced by the fact that many system administrators may not be aware of the specific locations where SESU searches for DLLs, making detection and prevention more challenging.
Mitigation strategies for CVE-2018-7799 should focus on both immediate remediation and long-term security improvements. The primary recommendation is to upgrade to SESU version 2.2.0 or later, which includes proper DLL loading security measures and validation mechanisms. Organizations should also implement strict access controls and file system permissions to prevent unauthorized DLL placement in directories searched by the update utility. Network segmentation and monitoring can help detect suspicious file placement activities that might indicate exploitation attempts. Additionally, implementing application whitelisting policies can prevent unauthorized DLLs from executing, even if they are successfully placed in the system. The vulnerability highlights the importance of proper software development security practices, particularly around dynamic library loading and privilege management. Organizations should also consider implementing security awareness training for system administrators to recognize potential exploitation attempts and maintain proper system hygiene. Regular vulnerability assessments and penetration testing should include checks for similar insecure library loading patterns across all software applications. The remediation process should also involve thorough system auditing to identify any potential compromise that may have occurred before the patch was applied. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date software and implementing defense-in-depth strategies to protect against sophisticated attack vectors that exploit fundamental security flaws in system components.