CVE-2017-2790 in Ichitaro Office
Summary
by MITRE
When processing a record type of 0x3c from a Workbook stream from an Excel file (.xls), JustSystems Ichitaro Office trusts that the size is greater than zero, subtracts one from the length, and uses this result as the size for a memcpy. This results in a heap-based buffer overflow and can lead to code execution under the context of the application.
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Analysis
by VulDB Data Team • 09/02/2020
The vulnerability identified as CVE-2017-2790 resides within JustSystems Ichitaro Office software when processing Microsoft Excel files with specific workbook stream structures. This flaw manifests during the handling of record type 0x3c within .xls file formats, representing a critical heap-based buffer overflow condition that can be exploited for remote code execution. The vulnerability stems from improper input validation and memory management practices within the application's file parsing logic, specifically in how it handles the size parameter of the record structure.
The technical implementation of this vulnerability involves a classic buffer overflow scenario where the application assumes that the size field of a record type 0x3c contains a value greater than zero before proceeding with memory operations. When this assumption proves incorrect, the software subtracts one from the length value and subsequently uses this adjusted result as the parameter for a memcpy operation. This mathematical manipulation effectively creates a situation where the application attempts to copy data into a buffer that is smaller than the amount of data being copied, leading to memory corruption. The heap-based nature of this overflow indicates that the corrupted memory resides in the heap allocation area, which is particularly dangerous as it can affect critical application structures and potentially allow attackers to overwrite function pointers or other control data.
The operational impact of CVE-2017-2790 extends beyond simple memory corruption, as successful exploitation can result in arbitrary code execution within the context of the affected application. This means that an attacker who successfully triggers the vulnerability could gain full control over the system running Ichitaro Office, potentially leading to data theft, system compromise, or further network infiltration. The vulnerability is particularly concerning because it can be triggered through simple file manipulation, making it an attractive target for phishing campaigns or malicious file distribution. The attack vector requires no special privileges or complex conditions, as the vulnerability exists in the normal file processing workflow of the application.
Mitigation strategies for this vulnerability should focus on immediate patching of affected systems, as the primary solution involves applying vendor-provided security updates that correct the improper size validation and memory handling. Organizations should implement strict file validation policies, particularly for Excel files received from untrusted sources, and consider deploying application whitelisting solutions to prevent execution of potentially malicious files. Network-based protections such as intrusion detection systems can be configured to monitor for suspicious file processing patterns, though the vulnerability's nature makes it challenging to detect through network traffic analysis alone. The vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a technique that could be mapped to ATT&CK tactic TA0002 (execution) and technique T1059.007 (command and scripting interpreter: powershell), as exploitation could involve executing malicious code through compromised applications.
The broader implications of this vulnerability highlight the importance of robust input validation in office productivity software, where file parsing operations must account for malformed or malicious input. This flaw demonstrates how seemingly minor issues in memory management can result in critical security vulnerabilities, emphasizing the need for comprehensive security testing and code review processes. Organizations should also consider implementing sandboxing mechanisms for file processing operations and maintaining regular security assessments to identify similar issues in other applications that handle complex file formats. The vulnerability serves as a reminder that legacy applications and office suites require ongoing security attention, particularly when they continue to process older file formats that may contain inherent parsing vulnerabilities.