CVE-2025-30376: Heap-based Buffer Overflow in Microsoft Office Excel Leading to Potential System Compromise

Overview

CVE-2025-30376 is a high severity vulnerability present in Microsoft Office Excel. This vulnerability stems from a heap-based buffer overflow that could potentially allow unauthorized attackers to execute code locally on the victim’s system. It poses a significant threat to the security of sensitive data, as it may permit system compromise or data leakage.
The vulnerability is of particular concern due to the widespread usage of Microsoft Office Excel across industries and organizations of all sizes. The successful exploitation of this vulnerability could lead to significant breaches, putting personal, financial, and business-critical information at risk.

Vulnerability Summary

CVE ID: CVE-2025-30376
Severity: High – CVSS 7.8
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: Execution of unauthorized code leading to potential system compromise or data leakage.

Affected Products

Product | Affected Versions

Microsoft Office Excel | [Insert affected version]

How the Exploit Works

The vulnerability arises from a heap-based buffer overflow in Microsoft Office Excel. An attacker can exploit this by crafting a malicious Excel document that, when opened, overflows the buffer and allows the attacker to execute arbitrary code. This code execution happens within the security context of the current user, which could lead to unauthorized system access or data leakage if the user possesses elevated privileges.

Conceptual Example Code

A conceptual exploit might involve a malicious macro embedded within an Excel document. Once the document is opened and the macro is executed, it can result in buffer overflow. Here’s a concept of how this might look:

Sub MaliciousMacro()
Dim buffer As String
Dim overflow As String
' Fill the buffer with data
buffer = String(1, "A")
' Create an overflow string longer than the buffer can handle
overflow = String(2, "B")
' Cause the buffer overflow, leading to potential arbitrary code execution
buffer = overflow
End Sub

Mitigation Guidance

Users are advised to apply the vendor patch as soon as it becomes available for their version of Microsoft Office Excel. As a temporary mitigation strategy, deploying a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can help detect and prevent exploitation attempts. Additionally, it is recommended to exercise caution when opening Excel documents from untrusted sources and to disable macros by default.