CVE-2017-2910 in libxls
Summary
by MITRE • 12/02/2020
An exploitable Out-of-bounds Write vulnerability exists in the xls_addCell function of libxls 2.0. 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 • 12/12/2020
The CVE-2017-2910 vulnerability represents a critical out-of-bounds write flaw within the libxls library version 2.0, specifically within the xls_addCell function. This vulnerability falls under the CWE-787 category of out-of-bounds write conditions, where the software writes data past the boundaries of a fixed-length buffer. The libxls library serves as a crucial component for parsing microsoft excel files, making it a widely used dependency across various applications and systems. The flaw manifests when processing specially crafted xls files that contain malformed cell data structures, causing the application to write beyond allocated memory boundaries during cell addition operations.
The technical exploitation of this vulnerability occurs through a carefully constructed malicious xls file that manipulates the xls_addCell function's handling of cell data. When the library processes such malformed input, it fails to properly validate the bounds of cell data before writing to memory locations, resulting in memory corruption that can be leveraged for remote code execution. The vulnerability stems from inadequate input validation and boundary checking within the cell processing logic, allowing attackers to craft xls files that trigger the out-of-bounds write condition. This type of vulnerability is particularly dangerous because it can be triggered through simple file delivery mechanisms, requiring no complex interaction beyond the initial file processing.
The operational impact of CVE-2017-2910 extends far beyond individual system compromise, as it affects any application or service that relies on libxls for excel file processing. This includes web applications, document management systems, email servers, and various enterprise software solutions that handle excel file uploads. The remote code execution capability means that attackers can potentially gain full control over affected systems, leading to data theft, system compromise, and lateral movement within network environments. From an attack framework perspective, this vulnerability aligns with the ATT&CK technique T1059.007 for command and scripting interpreter and T1566 for spearphishing attachment, as it enables attackers to execute arbitrary code through malicious file delivery.
Mitigation strategies for this vulnerability require immediate patching of affected libxls installations to version 2.0 or later, which contains the necessary bounds checking fixes. Organizations should implement comprehensive input validation for all excel file processing operations, including file format validation, size limitations, and content sanitization. Network-based defenses such as email filtering and web application firewalls can help prevent the delivery of malicious xls files, while application-level sandboxing can limit the potential damage from successful exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date third-party libraries and implementing robust security practices for file processing operations, particularly those involving binary formats that require complex parsing logic. System administrators should conduct thorough vulnerability assessments to identify all systems using affected libxls versions and prioritize remediation efforts based on risk exposure and business criticality.