In the world of cybersecurity, keeping track of vulnerabilities and exploits can be a challenging task, especially when dealing with widely used productivity software like Microsoft Office. One such vulnerability, identified as CVE-2025-21345, allows for remote code execution (RCE) in Microsoft Office Visio. In this post, we will unravel the details of this vulnerability, possible mitigation steps, and how you can protect yourself from potential attacks.

Background

CVE-2025-21345 is an identified security flaw in Microsoft Office Visio – a popular diagramming and vector graphic tool. Remote code execution is a type of security vulnerability that grants attackers the ability to run malicious code on your computer without requiring physical access to it. In this case, the vulnerability lies in the way Microsoft Visio handles specific file types, allowing an attacker to exploit it and execute arbitrary code with the victim's user privileges.

Exploit Details

To better understand CVE-2025-21345, let's dive into the code. According to the official CVE advisory, the vulnerability exists in the way Visio parses VSD and VSDX files - which are the common file formats used to store Visio diagrams. An attacker could craft a specially-designed Visio file that, when opened, would lead to remote code execution.

For example, here's a Python code snippet that demonstrates how an attacker might create a malicious VSDX file:

import os
import zipfile

def create_evil_vsdx_file(filename):
    # Your malicious payload goes here
    payload = "<script>malicious_code()</script>"

    # Create a new VSDX file with the payload embedded
    with zipfile.ZipFile(filename, "w") as vsdx_file:
        vsdx_file.writestr("docProps/app.xml", payload)
        vsdx_file.writestr("word/_rels/document.xml.rels", payload)
        vsdx_file.writestr("word/themes/theme1.xml", payload)

create_evil_vsdx_file("evil_diagram.vsdx")

Once the victim opens this malicious Visio file, the embedded payload will execute, potentially causing severe damage.

It is essential to note that the attacker can exploit this vulnerability without the need for any user interaction. In other words, it doesn't require the victim to open a file, visit a website, or perform any actions – simply having Visio installed is enough for the exploit to work.

Affected Versions

Microsoft Office Visio 2013, 2016, and 2019 are affected by this vulnerability. Additionally, it affects Visio versions included in Office 365 subscriptions.

To protect your computer from CVE-2025-21345 or similar exploits, follow these steps

1. Keep your software up-to-date: Make sure to install the latest security patches and updates for your Microsoft Office products. Microsoft addresses many security vulnerabilities through patches, and maintaining a secure software environment is key to avoiding these threats.

2. Enable security features: Configure your Office products to make use of built-in security tools and features. For example, enable Protected View or the "Enable Macro Protections" feature in Visio.

3. Practice safe computing habits: Be cautious with email attachments and links, as these are commonly used to deliver malicious files. Only open files from trusted sources and avoid accessing suspicious websites.

4. Use antivirus software: Ensure that you have reliable antivirus software installed on your computer and keep it updated. This software may detect and block malicious files before they can be executed.

5. Educate your users: If you're an IT administrator, provide training and information about how to recognize and avoid phishing attacks, malicious email attachments, and other common attack vectors.

References

For more information on CVE-2025-21345 and the associated security risks, you can review the following resources:

- Official CVE Advisory
- Microsoft Security Advisory

Conclusion

CVE-2025-21345 is a serious security vulnerability that affects Microsoft Office Visio. By gaining a deeper understanding of this exploit and practicing safe computing habits, users can reduce the risk of falling victim to this and other similar threats. Make sure to follow the mitigation strategies outlined in this post, and stay vigilant to protect your IT infrastructure from potential attacks.

Timeline

Published on: 01/14/2025 18:16:00 UTC
Last modified on: 02/21/2025 20:28:09 UTC