CVE-2025-26646: Microsoft Build Tools Path Traversal Flaw

CVE-2025-26646 Overview

External control of file name or path in .NET, Visual Studio, and Build Tools for Visual Studio allows an authorized attacker to perform spoofing over a network.

Critical Impact

This vulnerability allows an attacker to influence file paths, potentially leading to unauthorized file access and manipulation.

Affected Products

• Microsoft Build Tools
• Microsoft Visual Studio 2022
• Microsoft .NET

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Microsoft
• Not Available - CVE-2025-26646 assigned
• Not Available - Microsoft releases security patch
• 2025-05-13 - CVE-2025-26646 published to NVD
• 2025-07-10 - Last updated in NVD database

Technical Details for CVE-2025-26646

Vulnerability Analysis

The vulnerability occurs due to improper handling of external inputs affecting file paths in .NET, Visual Studio, and Build Tools for Visual Studio. An attacker exploiting this flaw can manipulate file locations, potentially leading to injection of malicious files or circumventing directory security settings.

Root Cause

The root cause is the lack of secure input validation for file and path names, allowing attackers to construct paths leading to unintended resources.

Attack Vector

The attack vector is through a network-based attack, where an attacker can send specially crafted inputs that are improperly sanitized by target applications.

// Example exploitation code (sanitized)
string path = "/home/user/" + input;
FileStream file = new FileStream(path, FileMode.Open);

Detection Methods for CVE-2025-26646

Indicators of Compromise

• Unexpected file modifications
• Suspicious network activity involving file operations
• Unauthorized access to critical file paths

Detection Strategies

Utilize behavioral analytics to detect anomalous file operations that don't fit normal usage patterns. Monitor specific directories commonly targeted for attacks and analyze logs for patterns of path traversal attempts.

Monitoring Recommendations

Implement real-time file monitoring with sentinel capabilities and use SentinelOne's XDR platform to detect abnormalities in file access patterns across Windows and Linux systems.

How to Mitigate CVE-2025-26646

Immediate Actions Required

• Review and sanitize user input affecting file paths
• Apply latest security patches provided by Microsoft
• Conduct a comprehensive security audit of file access controls

Patch Information

Administrators should apply the security patches made available by Microsoft, detailed in their security advisory.

Workarounds

As a temporary mitigation, limit file path inputs to trusted sources and ensure input validation strictly checks for unauthorized path traversal. Below is an example script to sanitize inputs:

# Configuration example
allowed_patterns="^(/[a-zA-Z0-9_-]+)+$"
if [[ $user_input =~ $allowed_patterns ]]; then
    echo "Valid input: $user_input"
else
    echo "Invalid input detected"
    exit 1
fi