CVE-2025-29979: Heap-based Buffer Overflow Vulnerability in Microsoft Office Excel

Overview

The Common Vulnerabilities and Exposures (CVE) system has cataloged a significant security flaw in Microsoft Office Excel, identified as CVE-2025-29979. This vulnerability is a heap-based buffer overflow issue, which could allow an unauthorized attacker to execute code locally on an affected system. Given the widespread use of Microsoft Office Excel, this vulnerability presents a significant risk to many organizations and individual users. It is especially concerning because it could potentially lead to a full system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-29979
Severity: High (7.8 CVSS Score)
Attack Vector: Local
Privileges Required: Low
User Interaction: Required
Impact: System compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Office Excel | All versions prior to vendor patch

How the Exploit Works

This vulnerability occurs due to the application’s failure to properly manage memory when processing certain data within an Excel spreadsheet. If manipulated correctly, this flaw can lead to a heap-based buffer overflow, enabling an attacker to execute arbitrary code on the affected system. The attacker would need to craft a malicious Excel file and convince the victim to open it.

Conceptual Example Code

While the exact exploit code would be specific to the vulnerability and the attacker’s intent, a conceptual example might involve embedding a malicious macro within an Excel file.

Sub Auto_Open()
Shell("cmd.exe /C arbitrary_code_here", vbHide)
End Sub

In this example, the `Shell` function is used to initiate a command prompt (`cmd.exe`) that executes the attacker’s arbitrary code when the Excel file is opened. This is a simplistic example and real-world exploits might be more complex and obfuscated to evade detection.

Recommended Mitigation

The primary mitigation for this vulnerability is to apply the vendor-provided patch. This will correct the memory management issue and eliminate the related buffer overflow vulnerability. As an interim measure, users can implement a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to detect and block attempts to exploit this vulnerability. However, this should not be considered a long-term solution, as it does not address the underlying flaw.