CVE-2018-12096 in liblnk
Summary
by MITRE
The liblnk_data_string_get_utf8_string_size function in liblnk_data_string.c in liblnk through 2018-04-19 allows remote attackers to cause an information disclosure (heap-based buffer over-read) via a crafted lnk file.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability identified as CVE-2018-12096 resides within the liblnk library, a critical component for parsing Windows shortcut files that are widely used in enterprise environments and digital forensics operations. This library serves as the foundation for handling lnk files which are essential for Windows file system navigation and application execution. The flaw manifests in the liblnk_data_string_get_utf8_string_size function located in the liblnk_data_string.c source file, representing a heap-based buffer over-read condition that can be exploited through maliciously crafted lnk files. The vulnerability affects all versions of liblnk up to and including the 2018-04-19 release, making it a significant concern for organizations that rely on this library for processing shortcut files.
The technical nature of this vulnerability stems from improper bounds checking within the string processing function that handles UTF-8 string size calculations. When a malicious lnk file is processed, the function fails to validate the boundaries of heap-allocated memory regions, allowing an attacker to manipulate the parsing logic and trigger a buffer over-read condition. This occurs because the function does not properly verify the length of input data before attempting to read from heap memory, creating a scenario where adjacent memory locations can be accessed and potentially exposed. The vulnerability operates at the memory management level and represents a classic heap-based buffer overflow pattern that can lead to information disclosure. According to CWE standards, this maps to CWE-125: Out-of-bounds Read, which specifically addresses situations where programs access memory beyond allocated boundaries. The underlying issue demonstrates poor input validation practices and inadequate memory boundary checking mechanisms that are fundamental requirements for secure software development.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it can provide attackers with access to sensitive data stored in adjacent memory regions. In enterprise environments where lnk files are frequently processed through automated systems, this vulnerability could enable attackers to extract confidential information including system paths, user credentials, or other sensitive data that may be stored in memory adjacent to the vulnerable buffer. The information disclosure could potentially reveal memory layout details that assist in further exploitation attempts, making this vulnerability particularly dangerous in targeted attacks. Digital forensics tools that rely on liblnk for lnk file analysis could also be compromised, potentially exposing forensic data or system information that should remain confidential. The vulnerability's remote exploitability means that attackers can leverage this weakness without requiring local access to the target system, making it a significant threat vector for network-based attacks. This aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and potentially T1552.001 for Unsecured Credentials, as the information disclosure could expose sensitive data that could be leveraged for further compromise.
Mitigation strategies for CVE-2018-12096 should prioritize immediate patching of affected liblnk installations, as the vulnerability has been addressed in subsequent releases. Organizations should implement comprehensive vulnerability management processes that include regular updates to all third-party libraries and components used in their systems. Input validation measures should be enhanced to include proper bounds checking and memory boundary verification in all string processing functions. Security monitoring should be implemented to detect unusual file processing patterns that might indicate exploitation attempts, particularly in environments where lnk files are frequently encountered. System administrators should also consider implementing file type restrictions and sandboxing mechanisms for lnk file processing to limit potential impact. The vulnerability highlights the critical importance of secure coding practices and proper memory management in open source libraries that are widely deployed across enterprise environments, emphasizing the need for regular security assessments of all third-party components used in production systems.