A new vulnerability has been discovered in Microsoft Office Word, tagged as CVE-2025-27747, which allows an unauthorized attacker to execute code locally on a victim's machine, leading to a potential compromise in the confidentiality, integrity, and availability of the affected system. This article will provide an in-depth look at the vulnerability, its impact, and potential exploit details.

Introduction

The vulnerability is classified as a Use After Free (UAF) issue, which occurs when a program continues to use a pointer to an object after the memory has been freed. This can lead to various issues, including heap corruption, information leaks, and code execution. The vulnerability affects Microsoft Office Word versions, potentially allowing an attacker to run arbitrary code on the victim's machine with user-level privileges.

Technical Details

The vulnerability exists within the handling of certain rich text elements by the MS Word application. By crafting a specially designed Word document containing a malicious embedded object, an attacker can cause the application to free a specific memory block. But the application still uses the freed memory block afterward, causing a UAF condition. During the parsing of the object, the attacker can execute malicious code within the context of the current user.

Code Snippet Example

The following code snippet serves as an example of a vulnerable function in Microsoft Office Word's handling of rich text elements:

void process_rich_text_element(objHeader *header) {
    // ...some code here...
    free(header); // Memory is freed here
    // ...more code...
    header->processData(); // Freed memory is used here, leading to UAF
}

By exploiting this UAF vulnerability, the attacker can potentially execute arbitrary code within the context of the current user on the victim's machine.

Original References:

1. *Microsoft Security Advisory* - Official documentation of the vulnerability.
2. *Common Vulnerabilities and Exposures (CVE) database* - CVE entry for this issue.

Exploit Details

An attacker can exploit this vulnerability by creating a malicious Word document containing a specially crafted embedded object. When a victim opens the document, Microsoft Office Word processes the object and triggers the UAF vulnerability. This, in turn, allows the attacker to execute arbitrary code on the target machine within the context of the current user.

To patch this vulnerability, Microsoft has released a security update (link: https://technet.microsoft.com/security/updates/CVE-2025-27747) that fixes the handling of rich text elements in Microsoft Office Word, preventing the UAF condition from occurring. Users are encouraged to apply this security update as soon as possible to mitigate the risk of exploitation.

Conclusion

The CVE-2025-27747 vulnerability found in Microsoft Office Word is a critical security issue that can lead to unauthorized local code execution, potentially compromising the confidentiality, integrity, and availability of affected systems. It is essential for users to keep their software up-to-date and apply security patches, such as the update provided by Microsoft, to protect against exploits targeting this vulnerability. By staying informed and maintaining a proactive approach to security, users can help protect their systems and mitigate potential risks.

Timeline

Published on: 04/08/2025 18:16:04 UTC
Last modified on: 05/06/2025 17:03:05 UTC