CVE-2025-47173: Microsoft Office Input Validation Vulnerability Leading to Local Code Execution

Overview

In this post, we’re exploring a significant cybersecurity vulnerability identified as CVE-2025-47173. This vulnerability lies within Microsoft Office, a suite of productivity applications used by millions of individuals and businesses worldwide. This flaw stems from improper input validation, allowing an attacker to execute code locally and potentially compromise the system or cause data leakage. Such vulnerabilities are severe as they can lead to unauthorized access and manipulation of sensitive data, hence why it matters to both individual users and organizations alike.

Vulnerability Summary

CVE ID: CVE-2025-47173
Severity: High (7.8 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 before the latest patch

How the Exploit Works

The vulnerability lies in the way Microsoft Office validates user input. An attacker can exploit this by crafting malicious input that is not properly sanitized by the application. This could be in the form of a document or a script embedded within a document. When this document is opened by a victim, the embedded code is executed locally. This could lead to actions ranging from unauthorized data access to complete control over the system depending on the user’s privileges.

Conceptual Example Code

Below is a conceptual example of how the vulnerability might be exploited using a macro embedded in an Office document:

Sub Auto_Open()
Dim cmd As String
cmd = "Shell(""cmd.exe /c echo This is a test > C:\test.txt"", vbNormalFocus)"
Call VBA.Interaction.CallByName(Application, cmd, VBA.CallType.Method)
End Sub

This example showcases an Office macro that, when opened, will execute a command using the Windows command prompt. This is a benign example, writing “This is a test” to a text file in the root of the C drive, but it demonstrates how an attacker could execute arbitrary commands.

Mitigation Guidance

Users are advised to apply the vendor-provided patch immediately to mitigate this vulnerability. In the absence of a patch, the use of Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) can provide temporary mitigation. These systems can detect and block attempts to exploit known vulnerabilities, providing an added layer of security. However, these are not foolproof, and applying the vendor patch remains the most effective solution.
It is also recommended to be cautious when opening Office documents from unknown sources and to disable macros where possible, as these are commonly used as an attack vector. It’s important to keep your software updated and follow best practices for cybersecurity to reduce your risk of exploitation.