CVE-2016-4290 in Office
Summary
by MITRE
When opening a Hangul HShow Document (.hpt) and processing a structure within the document, Hancom Office 2014 will attempt to allocate space for a block of data within the file. When calculating this length, the application will use a value from the file and add a constant to it without checking whether the addition of the constant will cause the integer to overflow which will cause the buffer to be undersized when the application tries to copy file data into it. This allows one to overwrite contiguous data in the heap which can lead to code-execution under the context of the application.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/20/2025
The vulnerability described in CVE-2016-4290 represents a classic buffer overflow condition that occurs within Hancom Office 2014 when processing specially crafted Hangul HShow Document files with the .hpt extension. This flaw exists in the memory management routines responsible for handling data structures within these documents, specifically when the application attempts to allocate memory for data blocks based on values read from the file. The vulnerability manifests during the file parsing phase where the software reads structural data from the .hpt file and calculates the required buffer size for subsequent data operations.
The technical implementation of this vulnerability involves an integer overflow condition that occurs when the application performs arithmetic operations on size values extracted from the malicious file. The software retrieves a value from the document structure and adds a constant to it to determine the buffer size needed for data copying operations. However, the application fails to validate whether this arithmetic operation results in integer overflow, allowing the calculated buffer size to become significantly smaller than required. This undersized buffer directly leads to memory corruption when the application attempts to copy data from the file into the improperly sized memory block.
From an operational perspective, this vulnerability creates a severe remote code execution risk that can be exploited by attackers who craft malicious .hpt files. The heap-based buffer overflow allows attackers to overwrite contiguous memory regions, potentially corrupting critical data structures or injecting executable code that will run under the privileges of the Hancom Office application. The attack surface is particularly concerning as it leverages legitimate file processing functionality, making it difficult to distinguish between benign and malicious documents at runtime. The vulnerability is classified under CWE-190 as an integer overflow condition, specifically involving an integer that is incremented, which aligns with the described behavior of adding a constant to a value from the file.
The exploitation of this vulnerability follows typical heap-based attack patterns that align with techniques documented in the MITRE ATT&CK framework under the Tactic of Execution and Defense Evasion. Attackers can craft .hpt files that, when opened by an unsuspecting user, trigger the vulnerable code path and enable arbitrary code execution. The impact extends beyond simple privilege escalation as the vulnerability can be leveraged in phishing campaigns, targeted attacks against specific organizations, or as part of broader attack chains where initial access is achieved through social engineering or other vectors. Organizations using Hancom Office 2014 are particularly at risk since this vulnerability affects the core document processing functionality that users expect to handle various file types without additional security concerns.
Mitigation strategies for CVE-2016-4290 should focus on both immediate patching and operational security measures. The primary recommendation is to apply vendor-provided security updates that address the integer overflow condition in the memory allocation routines. Organizations should also implement defensive measures such as restricting user permissions when opening office documents, employing sandboxing technologies for document processing, and deploying network-based intrusion detection systems to monitor for exploitation attempts. Additionally, security awareness training should emphasize the importance of not opening untrusted documents from unknown sources, as this vulnerability can be effectively exploited through social engineering campaigns that deliver malicious .hpt files via email attachments or malicious websites. The vulnerability highlights the critical importance of proper input validation and integer overflow checking in security-critical applications, particularly those that process untrusted data from external sources.