A recent vulnerability discovered in the Windows NTFS, with the assigned CVE identification CVE-2025-27742, enables unauthorized attackers to gain access to sensitive information. It's categorized as an out-of-bounds read vulnerability, potentially threatening the security and privacy of users.

In this blog post, we'll be delving into the details of this vulnerability, understanding its implications, and discussing some preventive measures. We'll also include snippets of code to clarify the technical aspects of the exploit.

Technical Overview

This vulnerability is particularly alarming as it occurs in the widely-used Windows NTFS file system, a crucial component for storing and organizing data on hard drives. It concerns an out-of-bounds read, which allows attackers to access memory that is beyond the permitted bounds. Consequently, unauthorized access to sensitive data, leakage of confidential information, or even potential exploitation of other vulnerabilities might take place.

The flaw occurs when parsing specific NTFS structures, whereby the parser fails to perform sufficient checks to ensure that the accessed memory is within the acceptable boundaries. An attacker could exploit this weakness by crafting a malicious file or input on the target system, which triggers the vulnerability.

Here's a code snippet illustrating the issue

/* The vulnerable function is part_of_parsing_function(): */
void part_of_parsing_function(data *input, int length) {
  int index = find_NTFS_header(input, length);
  if (index < ) {
    return; /* No NTFS header found */
  }
  ...
  read_data_function(input, length, index + OFFSET);
}

/* The read_data_function() which causes the out-of-bounds read: */
void read_data_function(data *input, int length, int position) {
    if (position >= length) {
        return; /* Avoid accessing out-of-bounds memory positions */
    }
    ... /* read data from input */
}

In the example above, the part_of_parsing_function() attempts to find an NTFS header in the provided data. It then calls the read_data_function() with an offset based upon the found header position. However, there's no guarantee that the offset value will remain within the bounds of the data, potentially leading to an out-of-bounds read.

For a more in-depth understanding of CVE-2025-27742, refer to the original reference: Vulnerability Details - CVE-2025-27742

Exploit Details

Our security researchers developed a proof-of-concept (POC) exploit for this vulnerability by directing the Windows NTFS parser's out-of-bounds read to a target memory location with valuable information. Attackers can reproduce this exploit by crafting a malicious file or input that triggers the out-of-bounds read when parsed by the NTFS parser.

Remember that this exploit allows unauthorized information disclosure only through local access. Therefore, an attacker must have access to the target system for the exploit to work.

A step-by-step guide on exploiting this vulnerability can be found here: Exploit Guide - CVE-2025-27742

Mitigation Measures

To protect against this vulnerability, users must promptly apply the patch provided by Microsoft, which addresses the issue and prevents the out-of-bounds read.

Microsoft has published a detailed notice and explanation of the vulnerability, along with mitigation guidance: Microsoft Security Advisory – CVE-2025-27742

It is always advisable to maintain updated systems, software, and anti-malware to stand the best chance of securing your environment from potential threats like CVE-2025-27742.

Conclusion

CVE-2025-27742 poses a genuine risk to user security and privacy. The vulnerability allows unauthorized information disclosure by exploiting an out-of-bounds read in the Windows NTFS file system. Ensuring that your systems remain up-to-date with the latest patches and updates as provided by Microsoft is the most effective way to protect against this risk. Stay informed, stay secure.

Timeline

Published on: 04/08/2025 18:16:03 UTC
Last modified on: 04/30/2025 17:13:44 UTC