CVE-2023-51598 in Office
Summary
by MITRE • 05/03/2024
Hancom Office Word DOC File Parsing Use-After-Free Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Hancom Office Word. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the parsing of DOC files. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-20384.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/14/2025
The CVE-2023-51598 vulnerability represents a critical use-after-free flaw in Hancom Office Word's document parsing functionality that enables remote code execution through malicious DOC files. This vulnerability resides in the software's handling of Microsoft Word document format files, specifically when processing the structured data within these documents. The flaw manifests during the parsing phase where the application fails to properly validate object existence before executing operations on memory references. This type of vulnerability falls under the CWE-416 category, which specifically addresses use-after-free conditions where memory is accessed after it has been freed, creating opportunities for memory corruption and arbitrary code execution. The vulnerability operates at the intersection of software security and memory management, where improper validation leads to predictable memory access patterns that attackers can exploit.
The technical implementation of this vulnerability involves the application's document parser encountering a malformed or specially crafted DOC file that triggers improper memory management during object handling. When the parser processes certain document elements, it creates references to objects in memory without ensuring these objects remain valid throughout the processing lifecycle. This creates a window of opportunity where an attacker can manipulate the document structure to cause the parser to reference freed memory locations, leading to heap corruption. The vulnerability requires user interaction through either visiting a malicious webpage that hosts the exploit or opening a malicious DOC file, making it a client-side attack vector that leverages social engineering tactics. The attack chain typically begins with a user opening or downloading a crafted document, which then triggers the vulnerable parsing code path, ultimately leading to code execution with the privileges of the affected application process.
The operational impact of CVE-2023-51598 extends beyond simple remote code execution to potentially compromise entire user systems through privilege escalation and lateral movement. When exploited successfully, this vulnerability allows attackers to execute arbitrary code within the context of the Hancom Office Word application, which typically runs with the privileges of the logged-in user. The vulnerability's classification as a remote code execution flaw means that attackers can potentially compromise systems without physical access or direct network connectivity to the target machine. This vulnerability aligns with ATT&CK technique T1203, which covers exploitation for privilege escalation, and T1059, which covers command and scripting interpreter usage. The remote nature of the attack makes it particularly dangerous in enterprise environments where users may inadvertently access malicious content through email attachments, web downloads, or compromised websites. Organizations running Hancom Office Word are at risk of full system compromise, data exfiltration, and potential persistence mechanisms being established through the executed malicious code.
Mitigation strategies for CVE-2023-51598 should focus on both immediate defensive measures and long-term architectural improvements. Organizations should implement strict document validation policies that prevent the opening of untrusted or unknown document formats, particularly in enterprise environments where users may be exposed to malicious content through email or web browsing. The most effective immediate fix involves applying vendor-provided patches or updates that address the specific use-after-free condition in the document parsing code. Network-level defenses such as web application firewalls and content filtering systems can help detect and block malicious document downloads or access to compromised websites. Additionally, user education and awareness programs should emphasize the dangers of opening unexpected document attachments or visiting untrusted websites. Security teams should monitor for exploitation attempts through network traffic analysis and endpoint detection systems that can identify suspicious memory access patterns or code execution activities. The vulnerability's reliance on user interaction makes behavioral analysis and sandboxing approaches particularly valuable for detecting and preventing exploitation attempts before they can succeed in compromising systems.