CVE-2025-21354 in Office
Summary
by MITRE • 01/14/2025
Microsoft Excel Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 08/25/2025
Microsoft Excel remote code execution vulnerabilities represent critical security flaws that allow attackers to execute arbitrary code on target systems through malicious Excel files. These vulnerabilities typically arise from insufficient input validation and memory corruption issues within Excel's parsing mechanisms for various file formats including xls, xlsx, xlsm, and xltm. The underlying technical flaw often involves improper handling of malformed or specially crafted data structures within spreadsheet files, leading to buffer overflows, use-after-free conditions, or other memory corruption vulnerabilities that can be exploited to gain remote code execution privileges.
The operational impact of these vulnerabilities extends far beyond simple file corruption or application crashes. When successfully exploited, attackers can leverage these flaws to install malware, establish persistent backdoors, escalate privileges, and access sensitive data within the compromised system. The attack surface is particularly broad since Excel files are commonly shared via email attachments, document repositories, and web downloads, making them prime targets for phishing campaigns and supply chain attacks. These vulnerabilities often align with CWE-121 stack-based buffer overflow or CWE-787 out-of-bounds write conditions that enable attackers to overwrite critical memory locations and redirect program execution flow.
The exploitation techniques frequently follow patterns consistent with the attack kill chain methodology, beginning with initial compromise through social engineering or malicious file delivery, followed by code execution within the target environment. Attackers typically employ techniques such as shellcode injection, return-oriented programming, or direct memory manipulation to achieve their objectives while avoiding detection by security controls. The vulnerabilities often map to ATT&CK tactics including initial access through malicious files, execution via legitimate user processes, and privilege escalation when the compromised Excel process runs with elevated permissions.
Mitigation strategies should encompass multiple layers of defense including regular patch management, implementation of application control policies such as Microsoft AppLocker or similar solutions, email filtering and sandboxing of suspicious attachments, and network segmentation to limit lateral movement. Organizations must also implement strict file format validation procedures and educate users about the risks of opening untrusted Excel files from unknown sources. Security monitoring should focus on detecting unusual Excel process behavior, memory access patterns, and anomalous network connections that may indicate exploitation attempts. Additionally, maintaining up-to-date threat intelligence feeds and implementing endpoint detection and response solutions can help identify and contain exploitation activities before they result in significant damage to organizational assets.