CVE-2016-4291 in Office
Summary
by MITRE
When opening a Hangul HShow Document (.hpt) and processing a structure within the document, Hancom Office 2014 will use a field from the structure in an operation that can cause the integer to overflow. This result is then used to allocate memory to copy file data in. Due to the lack of bounds checking on the integer, the allocated memory buffer can be made to be undersized at which point the reading of file data will write outside the bounds of the buffer. This can lead to code execution under the context of the application.
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Analysis
by VulDB Data Team • 04/20/2025
CVE-2016-4291 represents a critical integer overflow vulnerability affecting Hancom Office 2014 when processing Hangul HShow Document files with the .hpt extension. This vulnerability resides in the document parsing mechanism where the application reads a field from an internal structure and uses it directly in memory allocation calculations without proper validation. The flaw occurs during the handling of malformed .hpt files that contain specially crafted integer values designed to trigger the overflow condition. The vulnerability is categorized under CWE-190 as an integer overflow in the computation of memory allocation size, which directly leads to memory corruption.
The technical execution of this vulnerability involves a classic buffer overflow scenario where an attacker crafts a malicious .hpt document containing an oversized integer value in a specific structure field. When Hancom Office 2014 processes this document, it computes the memory allocation size using the malformed integer, resulting in insufficient buffer allocation. Subsequently, when the application attempts to copy file data into this undersized buffer, it writes beyond the allocated memory boundaries. This memory corruption can be exploited to overwrite critical memory locations including return addresses or function pointers, potentially allowing arbitrary code execution with the privileges of the targeted application user.
The operational impact of CVE-2016-4291 extends beyond simple local privilege escalation as it provides a pathway for remote code execution through social engineering attacks targeting Hancom Office users. Attackers can distribute malicious .hpt documents via email attachments, malicious websites, or compromised file sharing platforms, making this vulnerability particularly dangerous in enterprise environments where document processing is common. The vulnerability affects systems running Hancom Office 2014, and given the application's widespread use in Korean business environments, the potential attack surface is significant. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could lead to full system compromise.
Mitigation strategies for CVE-2016-4291 should focus on immediate patching of Hancom Office 2014 to address the integer overflow condition in memory allocation calculations. Organizations should implement strict document validation policies that prevent processing of untrusted .hpt files, particularly when they originate from external sources. Network-based protections should include email filtering rules that block .hpt file attachments and web proxies that restrict access to potentially malicious file downloads. System administrators should also consider implementing application whitelisting controls that restrict execution of Hancom Office to trusted environments and disable unnecessary document processing features. Additionally, monitoring for unusual memory allocation patterns and buffer overflow attempts should be enabled through endpoint detection and response solutions to identify potential exploitation attempts. The vulnerability demonstrates the critical importance of input validation and bounds checking in preventing memory corruption exploits, aligning with security best practices outlined in OWASP Top Ten and NIST cybersecurity frameworks.