CVE-2017-2107 in 7-ZIP32.DLL
Summary
by MITRE
Untrusted search path vulnerability in Self-extracting archive files created by 7-ZIP32.DLL 9.22.00.01 and earlier allows remote attackers to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 12/21/2020
The vulnerability identified as CVE-2017-2107 represents a critical untrusted search path flaw within the 7-Zip self-extracting archive functionality, specifically affecting versions 9.22.00.01 and earlier. This issue manifests through the 7-ZIP32.DLL component which is responsible for handling self-extracting archives, creating a dangerous privilege escalation vector that remote attackers can exploit to execute arbitrary code with elevated privileges. The vulnerability stems from improper handling of dynamic library loading sequences during archive extraction processes, where the application fails to properly validate or restrict the search path used to locate required DLL modules.
The technical exploitation of this vulnerability occurs when a malicious actor places a specially crafted Trojan horse DLL in a directory that appears earlier in the system's search path than the legitimate 7-Zip DLLs. During the extraction process, the system's dynamic linker resolves library dependencies by searching through directories in a predetermined order, and when the malicious DLL is positioned in a location that gets searched before the legitimate 7-Zip components, it gets loaded and executed instead of the intended module. This behavior aligns with common software security weaknesses categorized under CWE-426 Untrusted Search Path, which specifically addresses the dangerous practice of allowing external code to be loaded from untrusted locations within the application's search path.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to execute arbitrary code with the privileges of the user running the 7-Zip extraction process. When users extract self-extracting archives from untrusted sources, they inadvertently create an opportunity for attackers to inject malicious code that will execute with elevated privileges, potentially leading to full system compromise. The vulnerability is particularly dangerous in enterprise environments where users may extract archives from email attachments, downloaded files, or network shares without proper security verification. This type of attack pattern corresponds to techniques described in the MITRE ATT&CK framework under T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, demonstrating how attackers can leverage legitimate system tools to achieve unauthorized access and control.
Organizations affected by this vulnerability should implement immediate mitigations including updating to 7-Zip versions 9.22.00.02 or later, which contain fixes addressing the untrusted search path issue. System administrators should also consider implementing additional security controls such as restricting write access to directories containing legitimate 7-Zip components, monitoring for suspicious DLL loading activities, and employing application whitelisting solutions to prevent execution of unauthorized DLLs. The vulnerability highlights the critical importance of proper DLL search path management and dynamic library loading practices in preventing privilege escalation attacks, making it essential for security teams to review and audit similar issues in other applications that handle dynamic library loading operations.