CVE-2012-1887 in Office
Summary
by MITRE
Use-after-free vulnerability in Microsoft Excel 2003 SP3, 2007 SP2 and SP3, and 2010 SP1, and Office 2008 and 2011 for Mac, allows remote attackers to execute arbitrary code via a crafted spreadsheet, aka "Excel SST Invalid Length Use After Free Vulnerability."
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Analysis
by VulDB Data Team • 09/14/2018
The CVE-2012-1887 vulnerability represents a critical use-after-free flaw in Microsoft Excel software across multiple versions including Excel 2003 SP3, 2007 SP2 and SP3, 2010 SP1, and Office 2008 and 2011 for Mac. This vulnerability falls under the CWE-416 category of Use After Free, which occurs when a program continues to reference memory after it has been freed, creating a dangerous condition that can be exploited by malicious actors. The flaw specifically manifests in the handling of Spreadsheet Template (SST) records within Excel's parsing mechanism, where an invalid length parameter triggers improper memory management that can be manipulated to achieve remote code execution.
The technical exploitation of this vulnerability involves crafting a malicious spreadsheet file that contains specially formatted SST records with invalid length values. When Excel processes this malformed data, it attempts to allocate memory for the SST record but fails to properly validate the length parameter, leading to a situation where memory is freed prematurely while the application continues to reference the freed memory locations. This memory corruption allows attackers to overwrite critical memory structures and potentially execute arbitrary code with the privileges of the targeted user. The vulnerability is particularly dangerous because it can be triggered through simple file opening operations, making it an ideal candidate for phishing attacks and malicious document delivery methods.
From an operational perspective, this vulnerability presents significant risks to enterprise environments where Excel is widely used for document sharing and collaboration. The remote execution capability means that attackers can compromise systems without requiring local access or physical presence, making it particularly attractive for large-scale attacks. The vulnerability affects multiple versions of Microsoft Office, expanding the potential attack surface considerably and complicating mitigation efforts. Organizations using older versions of Excel without proper patching are especially vulnerable, as these systems lack the memory safety improvements introduced in later security updates. The attack vector through crafted spreadsheets aligns with common social engineering techniques, making it difficult to defend against through traditional network security measures alone.
Effective mitigation strategies for CVE-2012-1887 require a multi-layered approach combining immediate patching with operational security controls. Microsoft released security updates that addressed the memory management issues in affected Excel versions, and organizations should prioritize applying these patches to all vulnerable systems. Network-based defenses including email filtering and file validation can help prevent malicious documents from reaching end users, though these measures are not foolproof given the sophisticated nature of modern phishing campaigns. System hardening techniques such as disabling automatic execution of macros and implementing strict file type restrictions can reduce the attack surface. Additionally, security awareness training for end users helps identify potentially malicious documents before they are opened, while regular security assessments can identify systems that may have been overlooked during patch management processes. The vulnerability demonstrates the importance of maintaining up-to-date security patches and the need for comprehensive security frameworks that address both technical flaws and human factors in cybersecurity defense.