CVE-2008-4019 in Excel
Summary
by MITRE
Integer overflow in the REPT function in Microsoft Excel 2000 SP3, 2002 SP3, 2003 SP2 and SP3, and 2007 Gold and SP1; Office Excel Viewer 2003 SP3; Office Excel Viewer; Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Gold and SP1; Office SharePoint Server 2007 Gold and SP1; Office 2004 and 2008 for Mac; and Open XML File Format Converter for Mac allows remote attackers to execute arbitrary code via an Excel file containing a formula within a cell, aka "Formula Parsing Vulnerability."
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Analysis
by VulDB Data Team • 08/18/2019
The CVE-2008-4019 vulnerability represents a critical integer overflow flaw within Microsoft Excel's REPT function implementation across multiple versions of the office suite. This vulnerability stems from improper input validation and arithmetic handling within the formula parsing engine, specifically when processing the REPT function which repeats text a specified number of times. The flaw manifests when Excel encounters a formula containing the REPT function with an excessively large multiplier value that causes integer overflow during calculation, resulting in unpredictable memory behavior and potential code execution.
The technical implementation of this vulnerability involves the manipulation of the REPT function's parameter handling within Excel's parsing architecture. When the function receives a multiplier value that exceeds the maximum representable integer value, the arithmetic overflow corrupts adjacent memory locations, potentially allowing attackers to overwrite critical program structures or inject malicious code into the execution flow. This type of vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses the improper handling of integer arithmetic operations that can lead to buffer overflows and arbitrary code execution. The vulnerability operates at the application layer within the Microsoft Office suite, specifically targeting the Excel component's formula evaluation engine.
From an operational perspective, this vulnerability poses significant risks to enterprise environments where Excel files are frequently shared and opened by users. Attackers can craft malicious Excel files containing specially crafted REPT function formulas that, when opened by vulnerable versions of Excel, trigger the integer overflow condition. The exploit requires no special privileges beyond normal user access to execute successfully, making it particularly dangerous in targeted attack scenarios. The vulnerability affects a broad range of Microsoft Office products including various service packs and versions, extending its impact across multiple deployment environments and user groups. According to ATT&CK framework, this represents a technique categorized under T1059.005 - Command and Scripting Interpreter: Visual Basic, as the exploitation leverages Excel's macro and formula capabilities to achieve code execution.
Mitigation strategies for CVE-2008-4019 primarily involve immediate patching of affected Microsoft Office versions through official security updates from Microsoft. Organizations should implement strict file validation policies that prevent execution of untrusted Excel files, particularly those containing complex formulas or macros. Network-level controls including email filtering and web proxy configurations can help block potentially malicious Excel files from reaching end users. Additionally, system hardening measures such as disabling the REPT function or limiting formula complexity in corporate environments can provide additional defense layers. The vulnerability also highlights the importance of maintaining current security patches across all Microsoft Office installations and implementing comprehensive vulnerability management processes that can quickly identify and remediate similar issues. Organizations should also consider implementing application whitelisting solutions that restrict execution of potentially vulnerable Office components and establish robust incident response procedures for handling potential exploitation attempts.