CVE-2019-16337 in Office
Summary
by MITRE
The hncbd90 component in Hancom Office 9.6.1.9403 allows a use-after-free via an unknown object in a crafted .docx file.
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Analysis
by VulDB Data Team • 05/11/2025
The vulnerability identified as CVE-2019-16337 resides within the hncbd90 component of Hancom Office version 9.6.1.9403, representing a critical use-after-free flaw that can be exploited through maliciously crafted .docx files. This issue demonstrates a fundamental memory management error where the application fails to properly handle object lifecycles during document processing, creating opportunities for arbitrary code execution. The vulnerability specifically affects the handling of unknown objects within Microsoft Office document formats, making it particularly dangerous in environments where users frequently open documents from untrusted sources.
The technical nature of this flaw aligns with CWE-416, which describes the use of freed memory condition where a program continues to reference memory that has already been deallocated. In the context of document processing applications like Hancom Office, this occurs when the hncbd90 component processes a crafted .docx file containing malformed object structures that trigger improper memory deallocation followed by subsequent access to the freed memory region. The vulnerability stems from inadequate input validation and memory management practices within the document parser, allowing attackers to manipulate the application's memory state through carefully constructed document content.
From an operational perspective, this vulnerability presents significant risks to organizations relying on Hancom Office for document processing tasks. Attackers can craft malicious .docx files that, when opened by unsuspecting users, trigger the use-after-free condition and potentially execute arbitrary code with the privileges of the affected user. The attack vector requires social engineering to convince users to open the malicious document, but once executed, the exploit can lead to full system compromise. This vulnerability impacts the integrity and confidentiality of document processing environments and represents a serious threat to enterprise security infrastructure where document collaboration is common.
Security mitigation strategies for CVE-2019-16337 should prioritize immediate patching of affected Hancom Office installations to version 9.6.1.9404 or later, which contains the necessary memory management fixes. Organizations should implement strict document validation policies, including sandboxed document processing environments and content filtering mechanisms that scan incoming documents for suspicious structures. Network-based security controls such as email filtering and web application firewalls should be configured to block or quarantine .docx files from untrusted sources. Additionally, user awareness training programs should emphasize the dangers of opening documents from unknown or untrusted sources, as this vulnerability requires user interaction to be exploited. The mitigation approach should align with ATT&CK technique T1204.002, which involves social engineering through malicious documents, by implementing both technical controls and user education to reduce the attack surface and prevent successful exploitation of this use-after-free vulnerability.