CVE-2009-3135 in Word
Summary
by MITRE
Stack-based buffer overflow in Microsoft Office Word 2002 SP3 and 2003 SP3, Office 2004 and 2008 for Mac, Open XML File Format Converter for Mac, Office Word Viewer 2003 SP3, and Office Word Viewer allow remote attackers to execute arbitrary code via a Word document with a malformed File Information Block (FIB) structure, aka "Microsoft Office Word File Information Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 02/27/2025
This vulnerability represents a critical stack-based buffer overflow affecting multiple versions of Microsoft Office Word and related applications. The flaw exists within the parsing mechanism of Word documents, specifically when processing the File Information Block structure that contains metadata about the document. Attackers can craft malicious Word documents with intentionally malformed FIB structures that trigger memory corruption during document processing. The vulnerability affects Office 2002 SP3 and 2003 SP3 on Windows platforms, along with Office 2004 and 2008 for Mac, the Open XML File Format Converter for Mac, and various Word Viewer versions. This issue falls under CWE-121 Stack-based Buffer Overflow, which is classified as a serious memory corruption vulnerability that can lead to arbitrary code execution. The attack vector is particularly dangerous because it can be exploited remotely through email attachments or web downloads, making it a prime target for phishing campaigns and drive-by downloads.
The technical exploitation of this vulnerability occurs when Microsoft Word attempts to parse the malformed File Information Block structure within a malicious document. During the parsing process, the application fails to properly validate the size and structure of the FIB data, leading to a situation where data written to the stack exceeds the allocated buffer space. This memory corruption can overwrite adjacent memory locations including return addresses and function pointers, allowing attackers to redirect execution flow to malicious code injected into the process memory. The vulnerability is particularly concerning because it requires no user interaction beyond opening the malicious document, making it highly effective for social engineering attacks. The flaw is consistent with ATT&CK technique T1204.002, which involves user execution of malicious documents, and T1059.001 for command and scripting interpreter usage in payload delivery.
The operational impact of this vulnerability extends beyond simple code execution to potentially compromise entire systems through privilege escalation and lateral movement. Once an attacker gains execution control through this vulnerability, they can establish persistent access, escalate privileges, and use the compromised system as a launch point for further attacks within the network. The affected applications are widely deployed across enterprise environments, making this vulnerability particularly attractive to threat actors seeking broad impact. Organizations running these legacy versions of Microsoft Office face significant risk, as the vulnerability exists in software that may not receive regular security updates. The exploitability of this vulnerability is further enhanced by the fact that many users expect to be able to open Word documents without security concerns, creating a false sense of safety that attackers can exploit. This vulnerability demonstrates the critical importance of keeping software updated and implementing defense-in-depth strategies including email filtering, application whitelisting, and network segmentation to limit the potential impact of such memory corruption flaws.
Microsoft addressed this vulnerability through security updates that improved input validation and buffer management within the Word document parsing engine. The fix involved implementing proper bounds checking on the File Information Block structure and ensuring that all data read from document headers is validated before processing. Organizations should prioritize patching affected systems and consider implementing additional security controls such as Office macro security restrictions, sandboxing for document processing, and regular security assessments to identify similar vulnerabilities in legacy applications. The vulnerability also underscores the need for comprehensive application security testing, particularly for legacy software that continues to be used in enterprise environments despite known security risks. Proper security hygiene including regular patch management, user awareness training, and network monitoring remains essential for protecting against this class of memory corruption vulnerabilities that continue to pose significant threats to organizational security.