CVE-2025-30381: A Critical Out-of-bounds Read Vulnerability in Microsoft Office Excel

Overview

CVE-2025-30381 is a significant cybersecurity vulnerability that affects Microsoft Office Excel, a widely used spreadsheet program. This vulnerability could allow an unauthorized attacker to execute code locally, potentially leading to system compromise or data leakage. As such, it poses a substantial threat to any organization or individual using affected versions of Microsoft Office Excel. The severity of this vulnerability is accentuated by its potential impacts, which range from unauthorized data access to full system compromise.

Vulnerability Summary

CVE ID: CVE-2025-30381
Severity: High – CVSS Score 7.8
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Office Excel | All versions prior to the latest patch

How the Exploit Works

At its core, CVE-2025-30381 is an out-of-bounds read vulnerability. This means that the software improperly verifies or handles data within its buffer boundaries. In this case, an attacker can exploit this flaw by tricking a user into opening a specially crafted Excel document that contains malicious code. When the affected software reads beyond the allocated buffer, it can cause the software to crash, potentially executing the attacker’s code in the process.

Conceptual Example Code

Consider the following conceptual Excel macro that represents how the vulnerability might be exploited. This is a hypothetical example and does not represent an actual exploit:

Sub MaliciousMacro()
Dim buffer(10) As Integer
Dim counter As Integer
' Fill the buffer with innocent data
For counter = 0 To 10
buffer(counter) = counter
Next counter
' Overflow the buffer
For counter = 0 To 11
buffer(counter) = counter ' This line causes out-of-bounds read
Next counter
' Execute malicious code after the crash
Shell("malicious_command")
End Sub

This example illustrates how a malicious actor could craft a macro to cause an out-of-bounds read, leading to potential code execution. It’s important to note that this is a conceptual example-actual exploit code would be more complex and designed to evade detection.

Mitigation Guidance

To protect against this vulnerability, it is recommended to apply the latest patches provided by Microsoft for Office Excel. As a temporary mitigation, users can employ a Web Application Firewall (WAF) or Intrusion Detection System (IDS). These systems can help detect and prevent malicious attempts to exploit this vulnerability. However, they are not a substitute for applying the necessary patches and ensuring your software is up-to-date.