CVE-2016-4293 in Office
Summary
by MITRE
Multiple heap-based buffer overflows in the (1) CBookBase::SetDefTableStyle and (2) CBookBase::SetDefPivotStyle functions in Hancom Office 2014 VP allow remote attackers to execute arbitrary code via a crafted Hangul Hcell Document (.cell) file.
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Analysis
by VulDB Data Team • 12/21/2020
The vulnerability identified as CVE-2016-4293 represents a critical heap-based buffer overflow condition affecting Hancom Office 2014 VP software, specifically within two distinct functions that handle document styling operations. This flaw exists in the CBookBase::SetDefTableStyle and CBookBase::SetDefPivotStyle methods, which are responsible for processing and applying default table and pivot table styles in Hangul Hcell Document files with the .cell extension. The vulnerability stems from inadequate bounds checking during memory allocation and data processing operations, creating opportunities for attackers to manipulate heap memory structures through maliciously crafted input files.
The technical implementation of this vulnerability involves the manipulation of memory allocation parameters within the document processing pipeline where the application fails to validate the size and boundaries of data structures before copying user-supplied input into fixed-size buffers. When a malicious .cell file is processed, the application's handling of table and pivot style definitions causes the heap memory to be overwritten beyond its allocated boundaries, potentially leading to memory corruption that can be exploited to execute arbitrary code. This type of vulnerability falls under CWE-121 heap-based buffer overflow classification, which is particularly dangerous because it allows attackers to overwrite adjacent memory locations and potentially redirect program execution flow.
The operational impact of this vulnerability extends beyond simple code execution, as it creates a remote code execution vector that enables attackers to compromise systems running affected Hancom Office software without requiring local access or user interaction beyond opening the malicious document. The attack scenario typically involves an attacker delivering a specially crafted .cell file through social engineering, email attachments, or compromised websites, where the vulnerability is triggered upon document opening. This vulnerability is particularly concerning in enterprise environments where document processing is common and where the software may be used to open untrusted documents from external sources, making it a prime target for advanced persistent threat actors seeking to establish persistent access to networked systems.
Mitigation strategies for CVE-2016-4293 should prioritize immediate software updates from Hancom to address the heap overflow conditions in the affected functions. System administrators should implement strict file type filtering and content validation policies to prevent execution of .cell files from untrusted sources, while also deploying network-based intrusion detection systems to monitor for potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) as it enables attackers to execute malicious code through document processing. Additionally, memory protection mechanisms such as address space layout randomization and data execution prevention should be enabled to reduce the effectiveness of exploitation attempts, while regular security assessments and vulnerability scanning should be conducted to identify similar memory corruption issues in other software components.