CVE-2025-29977: Use After Free Vulnerability in Microsoft Office Excel

Overview

A critical vulnerability has been identified in Microsoft Office Excel, a widely used spreadsheet application, which could potentially allow an unauthorized attacker to execute arbitrary code on a victim’s system. This flaw, assigned the identification number CVE-2025-29977, is a ‘use-after-free’ vulnerability, a type of security bug that can lead to malicious code execution or even total system compromise.
The vulnerability is of significant concern due to the widespread usage of Microsoft Office Excel across various fields including business, academia, and personal computing. The potential for data leakage or system compromise makes this vulnerability a pressing issue that requires immediate attention.

Vulnerability Summary

CVE ID: CVE-2025-29977
Severity: High (7.8/10)
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise and data leakage

Affected Products

Product | Affected Versions

Microsoft Office Excel | All versions prior to the patch

How the Exploit Works

The vulnerability arises from a use-after-free condition in Microsoft Office Excel. In a use-after-free scenario, a section of the memory is used after it has been freed, leading to unexpected behavior such as crashing the program or, in this case, allowing for arbitrary code execution.
The flaw can be exploited when an attacker tricks a user into opening a specially crafted Excel file containing malicious code. Once the file is opened, the code is executed locally, potentially leading to system compromise or data leakage.

Conceptual Example Code

Here is a
conceptual
example of how the vulnerability might be exploited:

# Command to open a malicious Excel file
open "/path/to/malicious/file.xls"

In this conceptual example, an attacker would craft a malicious Excel file and trick the user into opening it. Once opened, the malicious code contained within the file would execute, exploiting the use-after-free vulnerability.

Mitigation Guidance

To mitigate the effects of this vulnerability, users are strongly advised to apply the patch provided by Microsoft as soon as it is available. As a temporary measure, the use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can help detect and prevent exploitation attempts. Regularly updating and patching software can also go a long way in preventing such vulnerabilities from being exploited.