CVE-2017-10859 in i-filter
Summary
by MITRE
Untrusted search path vulnerability in "i-filter 6.0 installer" timestamp of code signing is before 23 Aug 2017 (JST) 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-2017-10859 represents a critical untrusted search path issue within the i-filter 6.0 installer component that stems from inadequate code signing practices and flawed trust assumptions in the software installation process. This vulnerability specifically affects systems where the installer's digital signature was issued before August 23, 2017, creating a window of opportunity for attackers to exploit the trust model that the installer relies upon. The core technical flaw manifests when the installer processes DLL files without proper validation of their origins, allowing malicious actors to place Trojan horse DLLs in directories that are searched before legitimate system directories, thereby enabling privilege escalation through the execution of malicious code with elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader system compromise and potential lateral movement within network environments. Attackers exploiting this vulnerability can manipulate the installation process to execute arbitrary code with the privileges of the logged-in user or system administrator, depending on the context in which the installer runs. This type of vulnerability aligns with CWE-427 Uncontrolled Search Path Element, which specifically addresses the dangerous practice of allowing applications to search directories in an uncontrolled manner that could include malicious content. The vulnerability also maps to ATT&CK technique T1068, which covers the use of privilege escalation techniques through exploitation of software vulnerabilities, and T1546.001, which covers changes to the Windows Registry to establish persistence mechanisms.
The technical exploitation of this vulnerability requires the attacker to place a malicious DLL in a directory that will be searched by the installer before legitimate system directories, taking advantage of the installer's trust in the code signing certificate that was valid before the specified date. This approach leverages the trust relationship between the installer and the system, where the installer assumes that any DLL loaded during its execution is legitimate due to the code signing certificate. The vulnerability is particularly dangerous because it can be exploited during routine software installation or update processes, making it difficult for users to distinguish between legitimate and malicious activities. Organizations with outdated i-filter installations or those that have not updated their code signing certificates since the vulnerable date are at heightened risk of exploitation.
Mitigation strategies for CVE-2017-10859 should focus on immediate certificate validation and installation process hardening. System administrators should ensure that all affected installations have been updated to versions with proper code signing certificates issued after the vulnerable date, and that the installer's search path is properly configured to prioritize system directories over user-controllable locations. The implementation of application whitelisting policies and strict directory permissions can prevent unauthorized DLL placement in critical installation paths. Additionally, organizations should conduct comprehensive vulnerability assessments to identify any systems running vulnerable versions of i-filter and implement network monitoring to detect suspicious installation activities. The remediation process should also include updating the code signing infrastructure to ensure that all future installations use certificates with proper validation dates and that the installation process validates DLL integrity through proper cryptographic means rather than relying on potentially outdated trust models.