CVE-2011-1986 in Excel
Summary
by MITRE
Use-after-free vulnerability in Microsoft Excel 2003 SP3 allows remote attackers to execute arbitrary code via a crafted spreadsheet, aka "Excel Use after Free WriteAV Vulnerability."
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Analysis
by VulDB Data Team • 03/19/2021
The CVE-2011-1986 vulnerability represents a critical use-after-free flaw in Microsoft Excel 2003 Service Pack 3 that enables remote code execution through malicious spreadsheet files. This vulnerability falls under the CWE-416 category of Use After Free, where a program continues to reference memory after it has been freed, creating opportunities for attackers to manipulate memory contents and execute arbitrary code. The vulnerability specifically affects the WriteAV component within Excel's handling of spreadsheet data structures, making it particularly dangerous in enterprise environments where Excel remains widely deployed.
The technical exploitation of this vulnerability occurs when a maliciously crafted spreadsheet file is opened by an unsuspecting user, triggering a memory management error that allows attackers to overwrite critical memory locations with malicious code. The flaw stems from inadequate input validation and memory management practices within Excel's parsing of specific data formats, particularly affecting how the application handles certain AV (Audio/Video) related data structures in spreadsheet files. Attackers can leverage this vulnerability to execute code with the privileges of the victim user, potentially leading to complete system compromise.
From an operational impact perspective, this vulnerability presents significant risks to organizations relying on Excel 2003, as it can be exploited through social engineering attacks involving malicious email attachments or compromised websites. The vulnerability's remote execution capability means that attackers do not require physical access to target systems, making it particularly dangerous in corporate networks where users frequently open spreadsheet files from untrusted sources. Security professionals should note that Excel 2003 reached end-of-life in 2014, yet many organizations continue to use it due to legacy application dependencies, amplifying the risk exposure.
Organizations should implement multiple layers of defense to mitigate this vulnerability, including immediate deployment of Microsoft security patches for Excel 2003, enhanced email filtering to block malicious spreadsheet attachments, and user education programs to prevent opening suspicious files. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) within the MITRE ATT&CK framework, demonstrating how use-after-free vulnerabilities can serve as initial access vectors for broader attack campaigns. Network segmentation and application whitelisting policies should be implemented to limit the potential impact of successful exploitation, while regular security assessments should identify remaining legacy systems that may be vulnerable to similar memory corruption issues.