CVE-2021-24070 in Office
Summary
by MITRE • 02/26/2021
Microsoft Excel Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-24067, CVE-2021-24068, CVE-2021-24069.
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Analysis
by VulDB Data Team • 05/22/2026
This vulnerability represents a critical remote code execution flaw in Microsoft Excel software that allows attackers to execute arbitrary code on affected systems. The vulnerability stems from improper input validation within Excel's handling of specific file formats, particularly those involving structured data processing and formula evaluation. When a user opens a maliciously crafted Excel file, the vulnerability can be triggered through the automatic parsing and execution of embedded code within the document structure. The flaw exists in the way Excel processes certain data types and metadata within spreadsheet files, creating opportunities for attackers to inject malicious code that executes with the privileges of the victim user. This vulnerability is particularly dangerous because it can be exploited through social engineering attacks where users are tricked into opening seemingly legitimate Excel documents that contain hidden malicious payloads.
The technical implementation of this vulnerability involves memory corruption issues within Excel's file parsing engine, specifically in how it handles complex data structures and formula calculations. Attackers can craft Excel files containing specially formatted data that causes buffer overflows or memory corruption when processed by the application. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which occurs when a program writes data beyond the allocated memory boundaries of a stack buffer. This type of vulnerability is particularly dangerous because it can be exploited to overwrite critical memory locations including return addresses or function pointers, allowing attackers to redirect program execution flow. The attack vector typically involves the exploitation of the application's macro processing capabilities or direct manipulation of internal data structures within Excel's document format parser.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and data exfiltration capabilities. Once successfully exploited, attackers can establish persistent access to affected systems, deploy additional malware payloads, and potentially escalate privileges to system-level access. The vulnerability affects multiple versions of Microsoft Excel across different operating systems, making it particularly widespread in enterprise environments where spreadsheet applications are commonly used for business operations. Organizations may experience significant disruption as users inadvertently open malicious files, leading to potential data breaches, system downtime, and financial losses. The vulnerability can be leveraged for advanced persistent threat campaigns where attackers establish backdoors and maintain long-term access to compromised networks.
Mitigation strategies for this vulnerability require a multi-layered approach combining immediate patch management with defensive measures and user education. Microsoft has released security updates and patches that address the underlying memory corruption issues in Excel's file processing routines, which should be deployed immediately across all affected systems. Organizations should implement strict file validation policies that prevent opening of untrusted Excel files, particularly those received via email or downloaded from unverified sources. Network-based defenses including email filtering systems and web application firewalls can help block malicious Excel files before they reach end users. User awareness training programs should emphasize the dangers of opening unexpected Excel attachments and the importance of verifying document sources. Additionally, implementing application whitelisting policies that restrict execution of unauthorized Excel macros and disabling macro execution by default can significantly reduce exploitation success rates. The vulnerability demonstrates the importance of maintaining up-to-date security patches and following secure coding practices that prevent buffer overflow conditions in software applications.