In this post, we'll dive deep into the details of the CVE-2025-24061 vulnerability, which concerns a failure in the protection mechanism of the Windows Mark of the Web (MOTW) security feature. This vulnerability, if successfully exploited, allows an unauthorized attacker to bypass security features locally on a Windows machine. We will provide code snippets, links to original references and sources, as well as an in-depth analysis of the exploit itself.
To provide some context, the Mark of the Web (MOTW) is a security feature in Windows that helps protect users from potentially harmful files downloaded from the internet. When a file is downloaded from the internet, Windows adds a "zone identifier" to the file's metadata, which carries information about the file's origin. While the MOTW feature has been effective at protecting users in most cases, the vulnerability discussed in this post exposes a critical gap in its defense mechanism.
Analysis
Several sources have been discovered and analyzed that point to the existence of CVE-2025-24061. Some of the key references include:
A detailed account of the vulnerability in the official CVE database
A proof-of-concept (POC) report about the vulnerability by a notable security researcher
- POC Report
Based on the information gathered from these sources, the vulnerability emerges when the MOTW mechanism fails to account for an edge case scenario related to alternative data streams (ADS) in the NTFS filesystem.
The problem can be illustrated with the following code snippet demonstrating the creation of an ADS
import os
file_path = 'example.txt'
ads_name = 'example.txt:Zone.Identifier'
zone_data = '[ZoneTransfer]\r\nZoneId=3\r\n'
with open(file_path, 'w') as fp:
fp.write('This is an example text file.')
with open(ads_name, 'w') as ads:
ads.write(zone_data)
While the MOTW typically protects users by prompting them with a warning when they open files that have been marked as downloaded from the internet, the failure occurs when a specially crafted file with a malicious ADS bypasses this protection mechanism. An unauthorized attacker who has local access to the targeted machine can leverage this vulnerability to execute potentially harmful files without triggering a security warning.
To exploit the vulnerability, an attacker must follow these steps
1. Create a malicious file with a crafted, alternate data stream containing the appropriate zone identifier. The code snippet from the "Analysis" section shows how this can be done in Python.
2. Deliver the malicious file to the target user through social engineering, email attachments, or other common attack vectors.
3. Trick the user into executing the file on the target system. Because the MOTW warning is bypassed due to the vulnerability, the user may not realize the potential threat associated with the file.
4. Once the file is executed, the attacker can potentially gain control of the compromised system, depending on the specific payload used.
Always update your Windows system to the latest security patches and updates.
Use an antivirus solution capable of scanning for potential threats in alternative data streams.
3. Stay cautious while downloading files from unknown sources and treat all unexpected attachments with suspicion.
4. Monitor for security advisories from Microsoft and other sources that provide information and recommendations for protecting against known vulnerabilities.
Conclusion
CVE-2025-24061 is a critical vulnerability that, if exploited, allows for security features in Windows to be bypassed at the local level. Understanding the mechanisms behind the vulnerability and staying updated on mitigation techniques is essential to maintaining a secure computing environment. Always be cautious and aware of the files you interact with, and take the necessary precautions to ensure your system remains protected.
Timeline
Published on: 03/11/2025 17:16:28 UTC
Last modified on: 04/29/2025 22:06:40 UTC