CVE-2025-30386: Critical Use After Free Vulnerability in Microsoft Office

Overview

The Common Vulnerabilities and Exposures (CVE) system has identified a critical security vulnerability, dubbed CVE-2025-30386, within Microsoft Office. This ‘Use After Free’ vulnerability could allow an unauthorized attacker to execute code locally, posing a significant threat to individual users and businesses alike. The severity and widespread use of the software mean that this vulnerability could potentially impact millions of systems globally, leading to potential system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-30386
Severity: Critical (8.4 CVSS score)
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Office | All versions prior to patch

How the Exploit Works

The CVE-2025-30386 vulnerability is a ‘Use After Free’ vulnerability. It involves an error in how Microsoft Office manages memory for certain objects. When an object is prematurely freed or deleted, but references to it are not properly cleared, an attacker can trick the software into using these references, leading to arbitrary code execution. This could potentially lead to complete system compromise if the executed code is malicious.

Conceptual Example Code

Below is a conceptual example of how the vulnerability might be exploited. In this context, an attacker might use a specially crafted Office document that contains malicious code:

# Pseudocode
class VulnerableObject:
def __init__(self):
self.data = "Important data"
vuln_obj = VulnerableObject()
del vuln_obj  # Object is deleted
# Yet, a reference to it is still kept
vuln_obj_ref = weakref.ref(vuln_obj)
# Attacker tricks software into using the dangling reference
exploit(vuln_obj_ref)

Please note, this is simplified pseudocode and is only meant to conceptually illustrate the vulnerability. The actual exploit would be more complex and would require a deep understanding of memory management in the target system.

Mitigation Guidance

All users of Microsoft Office are urged to apply the vendor-provided patch as soon as possible. This patch addresses the ‘Use After Free’ vulnerability and prevents potential exploitation. If immediate patching is not possible, users are advised to employ a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as a temporary mitigation. However, these measures are not foolproof, and patching is the most effective way to secure your system against this vulnerability.