Description

A critical zero-day vulnerability in the Windows Common Log File System (CLFS), identified as CVE-2025-29824, has been actively exploited by the ransomware group Storm-2460. This privilege escalation flaw enables attackers to gain system-level access, allowing full control over compromised devices. In response to targeted attacks against sectors such as IT, finance, and retail—impacting organizations in the U.S., Venezuela, Spain, and Saudi Arabia Microsoft issued urgent security updates on April 8, 2025. Attackers leveraged sophisticated techniques to deploy the PipeMagic malware, initially retrieving a malicious MSBuild file via certutil from a compromised domain. The payload was decrypted and executed through the EnumCalendarInfoA API callback. Once activated, PipeMagic exploited the CLFS vulnerability in memory using dllhost.exe, leveraging RtlSetAllBits and NtQuerySystemInformation to manipulate system tokens and extract kernel addresses an approach that fails on Windows 11 version 24H2. Indicators of exploitation included a CLFS BLF file (PDUDrv.blf). Following initial compromise, attackers injected malicious code into winlogon.exe and used procdump.exe to extract LSASS memory, enabling credential theft and the subsequent deployment of RansomEXX ransomware, which encrypted files and left ransom notes pointing to .onion domains. To mitigate this threat, Microsoft urges immediate patching and emphasizes that Windows 11 version 24H2 is resilient against this attack method. Organizations should enable cloud-based protection in Microsoft Defender, use Endpoint Detection and Response (EDR) in block mode, conduct automated investigations, and implement attack surface reduction rules to prevent exploitation of similar vulnerabilities.