CVE-2017-2897 in libxls
Summary
by MITRE
An exploitable out-of-bounds write vulnerability exists in the read_MSAT function of libxls 1.4. A specially crafted XLS file can cause a memory corruption resulting in remote code execution. An attacker can send malicious XLS file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 01/11/2023
The CVE-2017-2897 vulnerability represents a critical out-of-bounds write flaw within the libxls library version 1.4, specifically within the read_MSAT function responsible for parsing Microsoft Excel file structures. This vulnerability falls under the CWE-787 Out-of-bounds Write classification, where the software writes data past the boundaries of a prepared buffer, potentially corrupting adjacent memory regions. The libxls library serves as a popular open-source component for parsing excel files, widely used in various applications including web servers, document processing systems, and enterprise software platforms that handle file uploads and conversions.
The technical exploitation of this vulnerability occurs when a maliciously crafted XLS file is processed by the vulnerable library. During the parsing of the workbook's Master Sector Allocation Table structure, the read_MSAT function fails to properly validate array indices or buffer boundaries before writing data to memory locations. This allows an attacker to construct an XLS file with malformed sector allocation data that causes the function to write beyond allocated memory space, potentially overwriting critical program data, function pointers, or return addresses. The vulnerability's remote code execution potential stems from the fact that many applications relying on libxls for file processing may be accessible over networks, making automated exploitation feasible through web-based attack vectors.
The operational impact of CVE-2017-2897 extends significantly across various attack surfaces where libxls is integrated into software systems. Applications vulnerable to this issue include web applications that accept file uploads, document conversion services, enterprise content management systems, and automated report generation platforms. The ATT&CK framework categorizes this vulnerability under T1203 Exploitation for Client Execution and T1059 Command and Scripting Interpreter, as successful exploitation can lead to arbitrary code execution on the target system. The remote nature of the attack means that exploitation can occur without physical access to the target system, making it particularly dangerous for web-facing applications and services.
Mitigation strategies for CVE-2017-2897 should prioritize immediate software updates to libxls version 1.4.1 or later, which contains the necessary patches to address the out-of-bounds write condition. System administrators should implement strict file validation and sanitization measures, particularly for file upload functionalities, including MIME type checking, file format validation, and content scanning. Network-based defenses should include intrusion detection systems that can identify suspicious file upload patterns and malformed XLS file structures. Additionally, applications using libxls should implement proper memory protection mechanisms such as stack canaries, address space layout randomization, and heap metadata protection to reduce the effectiveness of potential exploitation attempts. The vulnerability demonstrates the importance of input validation and proper boundary checking in parsing libraries, particularly those handling binary file formats that are commonly used in web applications and enterprise systems.