Windows NTFS Local Code Execution Vulnerability Exploited in the Wild – CISA

Microsoft’s March 2025 Patch Tuesday has addressed a critical zero-day vulnerability, CVE-2025-24993, a heap-based buffer overflow in the Windows NT File System (NTFS).

Rated 7.8 on the CVSS scale, this flaw allows unauthorized attackers to execute arbitrary code locally by exploiting improper memory handling when users mount malicious Virtual Hard Disk (VHD) files.

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added the vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, mandating federal agencies to apply patches by April 1, 2025.

Exploit Mechanics and Attack Chain

The vulnerability stems from a heap-based buffer overflow (CWE-122) in NTFS, which manages file storage on Windows operating systems.

Attackers craft malicious VHD files—often disguised as legitimate documents—and trick users into mounting them via phishing campaigns or compromised USB drives.

Once mounted, the flawed NTFS driver fails to validate memory boundaries, enabling attackers to corrupt heap structures and execute code with local user privileges.

Key technical details:

• Trigger: Requires user interaction to mount a malicious VHD.
• Impact: Enables privilege escalation to SYSTEM-level access, a critical vector for ransomware or lateral movement.
• Exploitation Context: Often chained with other NTFS flaws (e.g., CVE-2025-24984, CVE-2025-24991) to bypass security controls and exfiltrate data.

Trend Micro researchers observed over 600 organizations targeted via similar attack chains, often pairing CVE-2025-24993 with Microsoft Management Console (MMC) exploits like CVE-2025-26633.

ESET linked the vulnerability to the PipeMagic backdoor, which uses Azure-hosted command-and-control servers to deploy payloads.

Mitigation and Industry Response

Microsoft’s patch resolves the buffer overflow by implementing stricter memory validation checks for VHD operations.

CISA emphasizes immediate action, advising organizations to:

1. Deploy March 2025 patches across all Windows systems, prioritizing servers and endpoints.
2. Segment networks to isolate legacy systems still using outdated file systems like FAT32.
3. Educate users to avoid mounting unsolicited VHD files, which are increasingly used in phishing campaigns.

Additional recommendations:

• Monitor for anomalous VHD file activity using endpoint detection tools.
• Apply Microsoft’s “Block Untrusted Fonts” and “Attack Surface Reduction” rules to limit lateral movement.

While no ransomware campaigns have been explicitly tied to CVE-2025-24993, its exploitation in multi-stage attacks highlights systemic risks.

As Tenable’s Satnam Narang noted, this marks the first NTFS zero-day since 2022 and underscores the urgency of patch compliance.

The convergence of file system vulnerabilities and privilege escalation flaws creates a ripe environment for enterprise breaches.

With CISA’s binding directive and Microsoft’s patches now available, organizations must act swiftly to mitigate this high-severity threat.

Continued vigilance against VHD-based social engineering remains critical to thwarting evolving attack methodologies.

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