Windows Critical Vulnerability
CVE-2025-21391 – Windows Storage Elevation of Privilege Vulnerability
Base Score: 7.1 HIGH | Published Date: 02/12/2025
Overview
CVE-2025-21391 is a high-severity elevation of privilege (EoP) vulnerability in the Windows Storage component. Exploitation allows a local attacker to escalate privileges from a low-integrity user account to SYSTEM-level access, potentially compromising the entire system.
Technical Details
The flaw resides in the Windows Storage driver (storport.sys), which mishandles IOCTL (Input/Output Control) requests due to insufficient validation of user-supplied buffers. Attackers can craft malicious IOCTL commands to trigger a buffer overflow, corrupting kernel memory and executing arbitrary code with elevated privileges.
Impact
Successful exploitation grants full system control, enabling attackers to install malware, exfiltrate data, or disable security tools. The vulnerability is locally exploitable, requiring an attacker to execute code on the target machine.
Mitigation
Microsoft addressed this vulnerability in the February 2025 Patch Tuesday update. Users should apply KB500XXXX immediately. Temporary workarounds include restricting user permissions and disabling unnecessary storage-related services via Group Policy.
Sample Scenario
A penetration tester discovers a vulnerable workstation in a corporate network. Using a low-privileged account, they run a custom exploit tool that sends a malformed IOCTL request to storport.sys. The driver fails to validate the buffer size, leading to a kernel-mode buffer overflow. The exploit overwrites a function pointer, redirecting execution to a payload that spawns a SYSTEM shell. The tester now has unrestricted access to the machine.
CVE-2025-21418 – Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
Base Score: 7.8 HIGH | Published Date: 02/12/2025
Overview
CVE-2025-21418 is a critical EoP vulnerability in the Windows Ancillary Function Driver (AFD), a kernel-mode component of WinSock. Exploitation allows attackers to gain SYSTEM privileges by exploiting improper memory handling in AFD.
Technical Details
The vulnerability stems from a use-after-free flaw in AFD’s handling of socket connections. When a socket is closed, AFD fails to release associated memory properly. Attackers can manipulate this race condition to inject malicious code into kernel-space memory, bypassing security checks.
Impact
This flaw enables full system compromise. Attackers can bypass sandboxes, hijack network traffic, or persist across reboots. The higher CVSS score reflects the potential for broader system disruption compared to CVE-2025-21391.
Mitigation
Patched in Microsoft’s February 2025 update (KB500XXXX). Organizations should also enforce strict application control policies to block unauthorized binaries from interacting with WinSock.
Sample Scenario
An attacker compromises a user’s account via phishing. They download a malicious script masquerading as a network diagnostic tool. The script opens and closes sockets rapidly, triggering the use-after-free condition in AFD. By reallocating freed memory with shellcode, the attacker gains kernel execution and deploys a rootkit, evading detection by endpoint protection.
Conclusion
Both vulnerabilities highlight risks in Windows kernel drivers, a common target for EoP attacks. While hypothetical, these scenarios align with historical patterns (e.g., CVE-2020-0796 for SMB, CVE-2021-24086 for AFD). Proactive patching and least-privilege enforcement remain critical defenses against such exploits.