Threat Intelligence Report: Windows CLFS Zero-Day Exploitation and PipeMagic Ransomware (CVE-2025-29824)

CISO Executive Summary #

Overview #

CVE-2025-29824 represents a critical zero-day privilege escalation vulnerability in the Windows Common Log File System (CLFS) that was actively exploited by the Storm-2460 threat group for targeted ransomware attacks. The vulnerability, a use-after-free flaw enabling SYSTEM-level privilege escalation, was leveraged through the sophisticated PipeMagic trojan to deploy RansomEXX ransomware against organizations across multiple sectors including IT, real estate, finance, and retail.

Impact #

The exploitation of CVE-2025-29824 enabled:

• Privilege Escalation: Attackers gained SYSTEM-level access on compromised Windows systems
• Ransomware Deployment: RansomEXX ransomware distributed across targeted networks
• Multi-Sector Targeting: Organizations in IT, real estate, financial services, and retail sectors compromised
• International Scope: Attacks spanning United States, Venezuela, Spain, and Saudi Arabia

Mitigation #

Critical actions for Windows environments:

1. Emergency Patching: Apply Microsoft’s April 8, 2025 Patch Tuesday updates immediately
2. PipeMagic Detection: Hunt for MSBuild processes executing suspicious payloads
3. Credential Protection: Monitor for LSASS dumping and credential harvesting activities
4. Ransomware Preparedness: Implement comprehensive backup and recovery procedures

Engineering Breakdown #

CVE Details #

• CVE ID: CVE-2025-29824
• Severity: Important
• CVSS Score: 7.8 (High)
• Vector: Local
• Access Complexity: Low
• Authentication: Low Privileges Required

Description #

CVE-2025-29824 is a use-after-free vulnerability in the Windows Common Log File System (CLFS) that allows local privilege escalation to SYSTEM level. The vulnerability affects Windows systems where attackers with low-level access can exploit the flaw to gain administrative privileges, enabling full system control and ransomware deployment.

Technical Analysis #

Microsoft Security Analysis #

According to Microsoft’s security blog, CVE-2025-29824 was discovered through post-compromise analysis of targeted ransomware attacks. Microsoft identified Storm-2460 as the threat actor responsible, linking the group to the RansomEXX ransomware operation.

SOC Prime Vulnerability Assessment #

SOC Prime’s analysis emphasizes the critical nature of CLFS vulnerabilities, noting their potential for widespread exploitation. The use-after-free condition in CLFS provides reliable privilege escalation, making it attractive for post-compromise activities.

Logpoint Detection Analysis #

Logpoint researchers provided comprehensive detection methodologies for identifying PipeMagic deployment and CVE-2025-29824 exploitation, focusing on MSBuild process anomalies and privilege escalation indicators.

Exploitation Details #

Attack Chain Methodology #

The Storm-2460 exploitation follows this sequence:

1. Initial Access: Compromise through various vectors (not specified in Microsoft’s analysis)
2. Payload Delivery: Certutil used to download malicious MSBuild file from compromised legitimate website
3. PipeMagic Deployment: MSBuild executes encrypted payload, unpacking PipeMagic trojan
4. Privilege Escalation: PipeMagic triggers CVE-2025-29824 exploitation for SYSTEM access
5. Credential Harvesting: Procdump.exe used to dump LSASS for credential extraction
6. Ransomware Preparation: Environment configured for RansomEXX deployment
7. Encryption and Extortion: Files encrypted with !READ_ME_REXX2!.txt ransom notes

PipeMagic Malware Analysis #

Technical Characteristics:

• Plugin-based trojan architecture
• MSBuild-based initial deployment
• Encrypted payload delivery mechanism
• Multi-stage execution process

Capabilities:

• Sensitive data harvesting
• Full remote access to infected systems
• Additional malicious payload deployment
• CVE-2025-29824 exploit integration

Historical Context:

• Active since 2022, discovered by Kaspersky researchers
• Previously exploited CVE-2025-24983 (Windows Win32 Kernel Subsystem)
• Associated with Nokoyawa ransomware attacks using CVE-2023-28252

Threat Actor Attribution #

Storm-2460 Profile #

Microsoft Attribution:

• Linked to RansomEXX ransomware operation
• Focus on post-compromise privilege escalation
• Sophisticated malware development capabilities
• Multi-stage attack methodology

Target Profile:

• Information Technology sector (United States)
• Real Estate sector (United States)
• Financial Services (Venezuela)
• Software companies (Spain)
• Retail sector (Saudi Arabia)

Operational Characteristics:

• Use of legitimate tools (certutil, procdump)
• Compromised legitimate websites for payload hosting
• Focus on credential harvesting before ransomware deployment
• Professional ransom note deployment

Impact Assessment #

Targeted Industries #

Information Technology (US):

• IT service providers
• Software development companies
• Technology consultancies

Real Estate (US):

• Property management firms
• Real estate investment companies
• Commercial property organizations

Financial Services (Venezuela):

• Banking institutions
• Financial service providers
• Investment firms

Other Sectors:

• Spanish software companies
• Saudi Arabian retail organizations

Attack Methodology #

The attacks demonstrate sophisticated post-compromise techniques:

• Living-off-the-land binary (LOLBin) usage
• Legitimate tool abuse for malicious purposes
• Multi-stage payload deployment
• Professional ransomware operation integration

Indicators of Compromise #

File System Indicators #

# PipeMagic-related files
%TEMP%\*.tmp (MSBuild files)
%APPDATA%\Microsoft\MSBuild\* (Suspicious MSBuild projects)
C:\Windows\Temp\procdump*.dmp (LSASS dumps)
!_READ_ME_REXX2_!.txt (Ransom notes)

Process Indicators #

# Suspicious process execution
MSBuild.exe executing from unusual locations
certutil.exe downloading from external sources
procdump.exe targeting lsass.exe
PowerShell execution with encoded commands

Network Indicators #

# Network activity patterns
Certutil downloads from compromised legitimate sites
Unusual outbound connections during off-hours
Data exfiltration patterns consistent with ransomware
Command and control communication

Recommendations for Organizations #

Immediate Response Actions #

1. Critical Patching: Deploy April 8, 2025 Windows security updates
2. PipeMagic Hunting: Search for MSBuild anomalies and encrypted payloads
3. Credential Security: Monitor for LSASS dumping activities
4. Backup Verification: Ensure ransomware-resilient backup systems

Detection Strategies #

Hunt Queries #

Organizations should implement detection for:

# MSBuild process monitoring
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | 
Where-Object {$_.Message -like "*MSBuild.exe*"}

# Certutil abuse detection
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | 
Where-Object {$_.Message -like "*certutil*" -and $_.Message -like "*urlcache*"}

# LSASS access monitoring
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4656} | 
Where-Object {$_.Message -like "*lsass.exe*"}

SIEM Rules #

# PipeMagic Detection Rule
title: PipeMagic Trojan Activity
description: Detects MSBuild executing encrypted payloads
detection:
  selection:
    Image: '*\MSBuild.exe'
    CommandLine: '*tmp*'
    ParentImage: '*certutil.exe*'
  condition: selection

Long-term Security Improvements #

1. Privilege Management: Implement Just-in-Time admin access
2. Application Control: Deploy strict application whitelisting
3. Network Segmentation: Isolate critical systems and limit lateral movement
4. Advanced EDR: Deploy behavioral-based detection systems

Ransomware Resilience #

Backup Strategy #

# 3-2-1-1 Backup Rule Enhancement
- 3 copies of critical data
- 2 different storage media types
- 1 offsite/cloud backup
- 1 offline/air-gapped backup

Recovery Procedures #

1. Isolation Protocols: Immediate network segmentation procedures
2. Forensic Imaging: Preserve evidence while containing threats
3. Recovery Testing: Regular restoration drills and validation
4. Communication Plans: Stakeholder notification procedures

Lessons Learned #

Zero-Day Exploitation Trends #

CVE-2025-29824 highlights several critical trends:

• Increasing use of CLFS vulnerabilities for privilege escalation
• Integration of zero-day exploits into ransomware operations
• Sophisticated multi-stage deployment methodologies
• Abuse of legitimate administrative tools

Defense Implications #

The attack demonstrates the importance of:

• Behavioral-based detection over signature-based approaches
• Comprehensive logging and monitoring of administrative tools
• Rapid patch deployment procedures for privilege escalation vulnerabilities
• Integration of threat intelligence into security operations

Conclusion #

The exploitation of CVE-2025-29824 by Storm-2460 represents a sophisticated ransomware operation leveraging zero-day privilege escalation capabilities. The use of the PipeMagic trojan as a delivery mechanism demonstrates the evolution of ransomware groups toward more advanced post-compromise techniques.

Organizations must prioritize immediate patching while implementing comprehensive detection capabilities for post-compromise activities. The professional nature of the RansomEXX operation and the targeted approach to specific industry sectors indicate a well-resourced threat actor with significant capabilities.

The incident reinforces the critical importance of defense-in-depth strategies, particularly focusing on privilege escalation prevention, credential protection, and ransomware-resilient backup systems. Security teams must maintain vigilance for both the technical indicators of PipeMagic deployment and the broader patterns of professional ransomware operations.

Stay Vigilant