Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally
Description
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally
AI Analyst Comment
Remediation
Apply vendor security updates immediately. Monitor for exploitation attempts and review access logs.
Executive Summary:
A high-severity vulnerability has been identified in Microsoft Excel, designated CVE-2025-62553. This flaw could allow an attacker to take full control of a user's computer if they are tricked into opening a specially crafted Excel file. Successful exploitation could lead to data theft, malware installation, or further network intrusion.
Vulnerability Details
CVE-ID: CVE-2025-62553
Affected Software: Microsoft Multiple Products
Affected Versions: See vendor advisory for specific affected versions
Vulnerability: The vulnerability is a "Use-After-Free" condition within Microsoft Office Excel. An attacker can exploit this by creating a malicious Excel spreadsheet that, when opened, causes the application to incorrectly handle memory. Specifically, the application attempts to access a portion of memory after it has been deallocated, which can lead to memory corruption. A skilled attacker can control this corruption to divert the application's execution flow, allowing them to run arbitrary code with the same permissions as the logged-in user.
Business Impact
This vulnerability is rated as High severity with a CVSS score of 7.8. If exploited, an attacker could gain control of an employee's workstation, leading to significant business risks. Potential consequences include the theft of sensitive corporate data, financial information, or employee credentials; the deployment of ransomware or other malware; and using the compromised system as a pivot point to attack other internal network resources. The widespread use of Microsoft Excel across the organization makes this a critical threat that could result in data breaches, financial loss, and reputational damage.
Remediation Plan
Immediate Action: Apply the security updates released by Microsoft immediately across all affected systems. Prioritize patching for workstations that handle sensitive data or belong to high-value targets. Concurrently, security teams should monitor for indicators of compromise and review system and application logs for any unusual activity related to Excel processes.
Proactive Monitoring: Security teams should actively monitor for suspicious child processes spawning from
EXCEL.EXE(e.g.,cmd.exe,powershell.exe,wscript.exe). Utilize Endpoint Detection and Response (EDR) solutions to detect anomalous memory usage or process behavior associated with Excel. Monitor for unusual network connections originating fromEXCEL.EXEto external IP addresses.Compensating Controls: If immediate patching is not feasible, implement the following controls:
Exploitation Status
Public Exploit Available: false
Analyst Notes: As of December 9, 2025, there are no known public proof-of-concept exploits or active exploitation campaigns targeting this vulnerability. However, due to the nature of the vulnerability (local code execution in a ubiquitous software product), it is highly probable that threat actors will reverse-engineer the patch and develop a functional exploit.
Analyst Recommendation
This vulnerability represents a significant risk to the organization due to its high severity and the widespread use of Microsoft Excel. Although this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog, its potential for abuse is high. It is strongly recommended that all affected systems are patched on an emergency basis. If patching is delayed, compensating controls must be implemented immediately to reduce the attack surface. Continuous monitoring for signs of exploitation should be a top priority for the security operations team.