CVE-2025-53738: High Severity Use After Free Vulnerability in Microsoft Office Word

Overview

The cybersecurity landscape is continually evolving, with new vulnerabilities being discovered and exploited by malicious actors. One such vulnerability is CVE-2025-53738, a use after free vulnerability present in Microsoft Office Word that may allow an unauthorized attacker to execute code locally. This vulnerability poses a substantial threat to users due to Microsoft Office’s widespread use in both business and personal settings. The potential impact includes system compromise and data leakage, which could have severe repercussions if sensitive personal or organizational data is involved.

Vulnerability Summary

CVE ID: CVE-2025-53738
Severity: High (7.8 CVSS Severity Score)
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Office Word | All versions prior to the patch

How the Exploit Works

The vulnerability is a result of a use after free condition present in Microsoft Office Word. In simple terms, this means that the application uses memory after it has been freed or deleted. This leads to a state where an attacker could manipulate the application into executing arbitrary code, thereby exploiting the vulnerability.
When a Word document is opened, certain objects are created in memory. If a specially crafted document is used by an attacker, these objects can be manipulated in such a way that they are freed but still referenced later on. This state is exploitable by an attacker to execute arbitrary code in the context of the current user.

Conceptual Example Code

Here is a conceptual example of how the vulnerability might be exploited. This is not actual code but serves to illustrate the principles of the exploit.

// Define malicious payload
char malicious_payload[] = "...";
// Open a Word document
Document doc = Application.Documents.Open("malicious.docx");
// The document contains a specially crafted object that gets freed
// but is later referenced due to the use after free vulnerability
Object obj = doc.Objects[0];
// The attacker's code replaces the freed memory
memcpy(obj, malicious_payload, sizeof(malicious_payload));
// The application now executes the attacker's code when referencing the object
doc.Execute();

It’s crucial to note that this vulnerability requires user interaction, such as opening a malicious Word document. As such, one of the primary defenses against this vulnerability is user awareness and caution when opening documents, particularly from unknown sources.

Mitigation Guidance

Users are advised to apply the vendor patch as soon as it is available. In the meantime, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation. Furthermore, users should be wary of opening Word documents from unknown or untrusted sources, as these could potentially contain the malicious payload designed to exploit this vulnerability.