CVE-2012-0185 in Excel
Summary
by MITRE
Heap-based buffer overflow in Microsoft Excel 2007 SP2 and SP3 and 2010 Gold and SP1, Excel Viewer, and Office Compatibility Pack SP2 and SP3 allows remote attackers to execute arbitrary code via a crafted spreadsheet that triggers incorrect handling of memory during opening, aka "Excel MergeCells Record Heap Overflow Vulnerability."
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Analysis
by VulDB Data Team • 03/24/2021
The CVE-2012-0185 vulnerability represents a critical heap-based buffer overflow affecting multiple Microsoft Office versions including Excel 2007 SP2 and SP3, Excel 2010 Gold and SP1, Excel Viewer, and the Office Compatibility Pack SP2 and SP3. This vulnerability operates through a sophisticated attack vector that leverages malformed spreadsheet files to exploit memory handling flaws during the document opening process. The flaw specifically manifests in the incorrect management of heap memory when processing the MergeCells record structure within excel files, creating a condition where attacker-controlled data can overwrite adjacent memory locations beyond the intended buffer boundaries. This type of vulnerability falls under the CWE-121 heap-based buffer overflow category, which is classified as a serious memory corruption issue that can lead to arbitrary code execution.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides remote attackers with the capability to execute arbitrary code with the privileges of the victim user. When a user opens a specially crafted malicious spreadsheet file, the vulnerable Excel application attempts to process the MergeCells record and encounters the buffer overflow condition. This condition allows attackers to manipulate memory contents in ways that can overwrite critical program execution pointers, function return addresses, or other control data structures. The vulnerability's remote exploitability means that attackers can deliver malicious files through email attachments, web downloads, or other network-based delivery mechanisms without requiring physical access to the target system. The ATT&CK framework categorizes this as a code execution technique through malicious document delivery, specifically utilizing the T1204.002 sub-technique involving legitimate program execution.
The technical exploitation of CVE-2012-0185 requires careful crafting of spreadsheet files that contain malformed MergeCells records designed to trigger the heap overflow condition during normal document processing operations. Attackers typically construct malicious files that contain oversized or malformed data structures within the MergeCells record, which causes the Excel application to allocate insufficient memory for the data structure. When the application attempts to copy or process this malformed data, the buffer overflow occurs in the heap memory region, potentially allowing attackers to inject and execute malicious code. The vulnerability's exploitation is particularly dangerous because it occurs during the normal document opening process, meaning users can be compromised simply by opening what appears to be a legitimate spreadsheet file. This makes the vulnerability particularly effective for social engineering attacks where users are tricked into opening malicious files, and the exploit can bypass many traditional security controls that focus on network-level threats rather than application-level memory corruption issues.
Mitigation strategies for CVE-2012-0185 should include immediate application of Microsoft security patches and updates, as well as implementing comprehensive email filtering and web content filtering solutions to prevent the delivery of malicious spreadsheet files. Organizations should also consider implementing application whitelisting policies that restrict the execution of unauthorized Office applications or document processing tools. Network segmentation and user access controls can help limit the potential impact of successful exploitation attempts, while regular security awareness training can help users identify and avoid potentially malicious spreadsheet files. The vulnerability demonstrates the importance of maintaining up-to-date software patches and the critical need for organizations to implement robust vulnerability management processes that can quickly identify and remediate similar memory corruption vulnerabilities across their software environments.