CVE-2025-2449: NI FlexLogger RCE Vulnerability

CVE-2025-2449 Overview

CVE-2025-2449 is a directory traversal vulnerability affecting NI FlexLogger that enables remote code execution. This vulnerability allows remote attackers to create arbitrary files on affected installations of NI FlexLogger through malicious URI file parsing. The flaw exists within the usiReg component and results from the lack of proper validation of user-supplied paths prior to using them in file operations.

User interaction is required to exploit this vulnerability—specifically, the target must visit a malicious page or open a malicious file. An attacker can leverage this vulnerability to execute code in the context of the current user, potentially leading to complete system compromise. This vulnerability was tracked as ZDI-CAN-21805 by the Zero Day Initiative.

Critical Impact

Remote attackers can achieve arbitrary code execution by exploiting improper path validation in URI file parsing, allowing the creation of malicious files on victim systems.

Affected Products

• NI FlexLogger 2024 Q1
• NI FlexLogger (all versions using vulnerable usiReg component)

Discovery Timeline

• 2025-03-18 - CVE-2025-2449 published to NVD
• 2025-08-18 - Last updated in NVD database

Technical Details for CVE-2025-2449

Vulnerability Analysis

The vulnerability stems from CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), commonly known as path traversal or directory traversal. The usiReg component in NI FlexLogger processes URI files without adequately sanitizing user-supplied path information. This allows an attacker to craft malicious URI files containing path traversal sequences (such as ../) that escape intended directory constraints.

When a user opens a malicious URI file or visits a webpage that triggers the vulnerable handler, the usiReg component processes the embedded paths without proper validation. The attacker can manipulate file paths to write arbitrary files to locations outside the intended directory structure, ultimately achieving code execution in the security context of the logged-in user.

Root Cause

The root cause is insufficient input validation within the usiReg URI file parsing component. The component fails to properly sanitize or restrict user-controlled path data before utilizing it in file system operations. Without adequate path canonicalization and boundary enforcement, directory traversal sequences bypass intended restrictions, allowing file writes to arbitrary filesystem locations.

Attack Vector

The attack requires user interaction and operates over the network. An attacker must craft a malicious URI file or webpage that, when opened by a victim using an affected NI FlexLogger installation, exploits the path traversal flaw in the usiReg component.

The attack flow involves:

1. Attacker creates a malicious URI file containing path traversal sequences targeting the usiReg handler
2. Victim is socially engineered to open the malicious file or visit a malicious webpage
3. NI FlexLogger's usiReg component parses the URI file without proper path validation
4. Arbitrary files are written to attacker-controlled locations on the filesystem
5. Attacker achieves code execution through strategically placed malicious files

Technical details and additional information can be found in the Zero Day Initiative Advisory ZDI-25-146.

Detection Methods for CVE-2025-2449

Indicators of Compromise

• Unexpected file creation in system directories or startup locations outside NI FlexLogger working directories
• Suspicious URI file access patterns or execution of URI files from untrusted sources
• Anomalous process behavior from NI FlexLogger or usiReg component writing to sensitive filesystem paths
• Evidence of path traversal sequences (../ or ..\\) in URI file contents or log entries

Detection Strategies

• Monitor file system activity for NI FlexLogger processes writing files outside expected application directories
• Implement application whitelisting to detect unauthorized executables created by the usiReg component
• Deploy endpoint detection rules to identify suspicious URI file handling patterns
• Analyze network traffic for malicious URI file downloads targeting NI FlexLogger handlers

Monitoring Recommendations

• Enable detailed file system auditing for directories commonly targeted by directory traversal attacks
• Configure alerting for NI FlexLogger processes accessing paths containing traversal sequences
• Implement behavioral analysis for the usiReg component to detect anomalous file operations
• Review user activity logs for suspicious URI file interactions or downloads from untrusted sources

How to Mitigate CVE-2025-2449

Immediate Actions Required

• Advise users not to open URI files from untrusted sources or visit suspicious webpages while using NI FlexLogger
• Implement application control policies to restrict URI file handler behavior
• Apply network segmentation to limit exposure of systems running vulnerable NI FlexLogger versions
• Monitor for vendor security updates and apply patches as soon as they become available

Patch Information

Refer to the Zero Day Initiative Advisory ZDI-25-146 for the latest information on patches and vendor remediation guidance. Contact NI directly for specific patch availability and instructions for updating NI FlexLogger to a version that addresses this vulnerability.

Workarounds

• Restrict URI file associations at the operating system level to prevent automatic handling by vulnerable components
• Implement strict email and web filtering to block potentially malicious URI files
• Use application sandboxing to isolate NI FlexLogger from critical system directories
• Educate users about the risks of opening URI files from unknown or untrusted sources

# Example: Restrict URI file handler association (Windows)
# Remove or modify usiReg URI handler registration
reg query "HKEY_CLASSES_ROOT\usiReg" /s
# Review and consider removing suspicious protocol handlers until patched