CVE-2006-3493 in Office
Summary
by MITRE
Buffer overflow in LsCreateLine function (mso_203) in mso.dll and mso9.dll, as used by Microsoft Word and possibly other products in Microsoft Office 2003, 2002, and 2000, allows remote user-assisted attackers to cause a denial of service (crash) via a crafted Word DOC or other Office file type. NOTE: this issue was originally reported to allow code execution, but on 20060710 Microsoft stated that code execution is not possible, and the original researcher agrees.
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Analysis
by VulDB Data Team • 07/12/2021
The vulnerability identified as CVE-2006-3493 represents a critical buffer overflow flaw within the Microsoft Office suite, specifically affecting versions 2000, 2002, and 2003. This issue resides in the LsCreateLine function located within the mso.dll and mso9.dll libraries, which are fundamental components of Microsoft Office's core functionality. The vulnerability manifests when processing maliciously crafted Word documents or other Office file formats, creating a scenario where remote attackers can exploit this weakness to disrupt system operations. The flaw operates through a classic buffer overflow mechanism where insufficient bounds checking allows an attacker to write beyond allocated memory boundaries, potentially leading to system instability and application crashes.
The technical implementation of this vulnerability stems from inadequate input validation within the LsCreateLine function, which handles line creation operations in Microsoft Office applications. When a malformed document is processed, the function fails to properly validate the size of incoming data structures, particularly those related to line formatting and document layout parameters. This deficiency creates an exploitable condition where malicious input can overwrite adjacent memory locations, corrupting program execution flow and ultimately causing application crashes. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which represents a well-documented class of memory corruption vulnerabilities that have historically been exploited for more severe attacks. The specific nature of the flaw means that it operates within the document processing pipeline where Office applications parse and render document content, making it particularly dangerous as it can be triggered simply by opening a malicious file.
The operational impact of this vulnerability extends beyond simple denial of service, as it demonstrates the inherent risks present in complex document processing systems that must handle diverse and potentially malicious input. When exploited, the buffer overflow causes Microsoft Word applications to crash immediately upon processing the malicious document, effectively creating a denial of service condition that prevents legitimate users from accessing their documents. This vulnerability particularly affects enterprise environments where Office applications are extensively used, as it could be leveraged by attackers to disrupt business operations or as part of larger attack campaigns. The flaw's remote nature means that attackers can deliver malicious documents through various vectors including email attachments, web downloads, or file sharing platforms without requiring local system access. The original classification as allowing code execution was later revised by Microsoft, indicating that while the vulnerability can cause system instability, it does not provide the means for arbitrary code execution, though it still represents a significant threat to system availability and user productivity.
Mitigation strategies for CVE-2006-3493 should focus on both immediate protective measures and long-term system hardening approaches. Microsoft released security patches and updates to address this vulnerability, which should be deployed immediately across all affected systems. Organizations should implement strict document validation policies, particularly for email attachments and external file transfers, using content filtering solutions that can detect and block potentially malicious Office documents. Network segmentation and access controls should be enhanced to limit exposure, while user education programs should emphasize the dangers of opening untrusted documents from unknown sources. The vulnerability's classification under ATT&CK technique T1203 - Exploitation for Client Execution highlights the importance of maintaining up-to-date security patches and implementing application whitelisting where possible. System administrators should also consider disabling unnecessary Office features and macros in environments where they are not required, as these additional attack vectors can compound the risks associated with document processing vulnerabilities. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of affected software versions, ensuring comprehensive protection against this and similar memory corruption vulnerabilities that continue to pose threats to enterprise environments.