CVE-2017-10855 in FENCE-Explorer
Summary
by MITRE
Untrusted search path vulnerability in FENCE-Explorer for Windows V8.4.1 and earlier allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 11/17/2019
The vulnerability identified as CVE-2017-10855 represents a critical untrusted search path flaw in FENCE-Explorer for Windows version 8.4.1 and earlier. This type of vulnerability falls under the CWE-426 category, which specifically addresses the execution of untrusted code due to improper handling of dynamic library loading. The issue manifests when the application fails to properly validate the source and integrity of dynamically loaded libraries, creating an avenue for privilege escalation attacks. The vulnerability is particularly concerning because it allows an attacker to place a malicious Trojan horse DLL in an unspecified directory, which the application will then load and execute with elevated privileges. This flaw directly violates the principle of least privilege and demonstrates poor input validation practices in the application's dynamic library resolution mechanism.
The technical exploitation of this vulnerability occurs through a classic DLL hijacking attack vector where the malicious DLL is placed in a directory that appears earlier in the system's search path than the legitimate application directories. When FENCE-Explorer attempts to load required libraries, it inadvertently loads the attacker-controlled DLL instead of the intended legitimate library. This behavior is consistent with CWE-787, which describes out-of-bounds writes that can lead to privilege escalation when combined with improper library loading sequences. The vulnerability's impact extends beyond simple code execution to full system compromise, as the loaded DLL can execute with the same privileges as the FENCE-Explorer application, potentially including administrative rights.
From an operational standpoint, this vulnerability creates significant risk for organizations using FENCE-Explorer, particularly in environments where the application runs with elevated privileges or has access to sensitive network resources. The attack requires minimal sophistication from the adversary, as it only requires placing a malicious DLL in an accessible directory, making it particularly dangerous in shared or multi-user environments. The unspecified directory aspect of the vulnerability suggests that the application's search path is either configurable or relies on default system paths that may be writable by unprivileged users. This vulnerability aligns with ATT&CK technique T1059.001, which covers execution through command and scripting interpreters, and T1068, which addresses privilege escalation through exploitation of system vulnerabilities. Organizations may face potential data breaches, system compromise, and unauthorized access to network resources if this vulnerability remains unpatched.
The recommended mitigation strategy involves immediate patching of the FENCE-Explorer application to version 8.5.0 or later, which addresses the untrusted search path vulnerability through proper library loading mechanisms. Additionally, implementing strict directory permissions and using tools such as Windows Defender Application Control or similar application whitelisting solutions can prevent unauthorized DLL loading. System administrators should also conduct comprehensive vulnerability assessments to identify other applications with similar search path issues and implement the principle of least privilege for all system applications. The vulnerability demonstrates the critical importance of secure coding practices and proper library loading procedures, particularly in security applications that handle sensitive data and network communications. Organizations should also consider implementing network monitoring to detect unusual DLL loading patterns that might indicate exploitation attempts.