CVE-2024-38030: Windows 10 1507 Spoofing Vulnerability

CVE-2024-38030 Overview

CVE-2024-38030 is a Windows Themes Spoofing Vulnerability that affects a wide range of Microsoft Windows operating systems, including Windows 10, Windows 11, and Windows Server editions. This vulnerability enables attackers to exploit the Windows Themes feature to potentially leak NTLM credentials by convincing users to open maliciously crafted theme files. When a user applies or previews a specially crafted theme file, Windows may attempt to authenticate to a remote server controlled by the attacker, inadvertently exposing the user's NTLM hash.

Critical Impact

This vulnerability can lead to unauthorized disclosure of sensitive NTLM credential hashes, which attackers can use for credential relay attacks, offline brute-force attacks, or pass-the-hash attacks to gain unauthorized access to systems and resources.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2, 23H2)
• Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022

Discovery Timeline

• July 9, 2024 - CVE-2024-38030 published to NVD
• September 15, 2025 - Last updated in NVD database

Technical Details for CVE-2024-38030

Vulnerability Analysis

This spoofing vulnerability resides in how Windows processes theme files (.theme files). Windows theme files can contain references to external resources, including network paths specified via UNC (Universal Naming Convention) paths. When a malicious theme file is opened or previewed, Windows may automatically attempt to authenticate to an attacker-controlled SMB server to retrieve the referenced resource.

The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). During the authentication attempt, Windows sends the user's NTLM hash to the remote server, which the attacker can capture. This leaked credential data can then be leveraged for various attack scenarios, including relay attacks against other network services or offline password cracking attempts.

The vulnerability requires user interaction—specifically, the user must open or preview a malicious theme file. However, theme files can be delivered through various vectors including email attachments, web downloads, or shared network locations, making social engineering attacks feasible.

Root Cause

The root cause of CVE-2024-38030 stems from insufficient validation and restriction of external resource paths within Windows theme files. The Windows Themes feature fails to adequately sanitize or block UNC paths that reference external network resources, allowing theme files to trigger outbound SMB authentication requests. This design flaw enables attackers to craft theme files that force the operating system to automatically connect to attacker-controlled servers when the theme is processed.

Attack Vector

The attack vector for CVE-2024-38030 is network-based and requires user interaction. An attacker crafts a malicious .theme file containing a UNC path pointing to an attacker-controlled SMB server. The attack flow typically proceeds as follows:

1. The attacker creates a theme file with embedded references to external resources via UNC paths (e.g., \\attacker-server\share\resource)
2. The malicious theme file is delivered to the victim through phishing emails, malicious websites, or shared network locations
3. When the victim opens or previews the theme file, Windows attempts to retrieve the referenced external resource
4. During this retrieval attempt, Windows performs NTLM authentication with the attacker's server
5. The attacker captures the victim's NTLM hash, which can be used for credential relay attacks or offline cracking

The vulnerability does not require any special privileges on the target system—standard user interaction is sufficient to trigger the credential leak.

Detection Methods for CVE-2024-38030

Indicators of Compromise

• Unexpected outbound SMB (port 445) or WebDAV connections to external or unknown IP addresses
• Theme files (.theme extension) received via email attachments or downloaded from untrusted sources
• Network logs showing authentication attempts to unfamiliar external servers
• Unusual activity in Windows Explorer related to theme file processing

Detection Strategies

• Monitor network traffic for outbound SMB connections (port 445) to external IP addresses, especially following user interaction with theme files
• Implement email gateway rules to scan and quarantine suspicious .theme file attachments
• Deploy endpoint detection rules to alert on theme files containing UNC paths to external servers
• Use SIEM correlation rules to detect patterns of outbound NTLM authentication attempts to non-corporate resources

Monitoring Recommendations

• Enable Windows Security Event logging for NTLM authentication events (Event ID 4624, 4648)
• Configure network monitoring to alert on SMB traffic destined for external networks
• Implement file integrity monitoring for the Windows Themes directory (%LocalAppData%\Microsoft\Windows\Themes)
• Review proxy and firewall logs for blocked outbound SMB connection attempts

How to Mitigate CVE-2024-38030

Immediate Actions Required

• Apply the latest Microsoft security updates for all affected Windows systems immediately
• Block outbound SMB traffic (port 445) at the network perimeter firewall for non-essential connections
• Educate users about the risks of opening theme files from untrusted sources
• Consider implementing Group Policy to restrict NTLM authentication to trusted servers only

Patch Information

Microsoft has released security updates to address CVE-2024-38030. Organizations should consult the Microsoft Security Response Center Advisory for specific patch information and download links for their affected Windows versions. Apply these updates through Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog based on your organization's patch management strategy.

Additional technical resources are available, including a Vicarius Detection Script and a Vicarius Mitigation Script to assist with vulnerability assessment and remediation.

Workarounds

• Block outbound SMB traffic (port 445) at the firewall to prevent NTLM credential leakage to external servers
• Configure Windows Group Policy to restrict NTLM usage by enabling "Network security: Restrict NTLM: Outgoing NTLM traffic to remote servers"
• Disable automatic preview of theme files in Windows Explorer where possible
• Implement email filtering rules to block or quarantine .theme file attachments

# Example: Group Policy configuration to restrict outbound NTLM traffic
# Navigate to: Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options
# Set "Network security: Restrict NTLM: Outgoing NTLM traffic to remote servers" to "Deny all"

# PowerShell command to check current NTLM restriction settings
Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0" -Name "RestrictSendingNTLMTraffic"