CVE-2025-21418: Windows 10 1607 Privilege Escalation Flaw

CVE-2025-21418 Overview

The CVE-2025-21418 vulnerability involves an elevation of privilege issue in the Windows Ancillary Function Driver for WinSock. This high-severity flaw allows local attackers to gain elevated privileges on affected systems, leveraging a memory-related issue within the driver function handling.

Critical Impact

Successful exploitation can lead to complete control over an affected system, allowing for unauthorized access and potential further privilege escalation.

Affected Products

• Microsoft Windows 10 1607
• Microsoft Windows 10 1809
• Microsoft Windows 11 22H2

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Microsoft
• Not Available - CVE CVE-2025-21418 assigned
• Not Available - Microsoft releases security patch
• 2025-02-11 - CVE CVE-2025-21418 published to NVD
• 2025-10-27 - Last updated in NVD database

Technical Details for CVE-2025-21418

Vulnerability Analysis

The vulnerability arises due to improper handling of input within the Windows Ancillary Function Driver for WinSock. An attacker exploiting this vulnerability could leverage unsanitized input to trigger unauthorized execution paths, leading to privilege escalation.

Root Cause

The core issue resides in a buffer overflow condition, where insufficient boundary checks on user inputs allow memory corruption, facilitating introduction of malicious code.

Attack Vector

The vulnerability is exploitable through a local attack vector, requiring an authenticated user to trigger the malicious input.

// Example exploitation code (sanitized)
#include <stdio.h>
#include <string.h>

void vulnerableFunction(char *input) {
    char buffer[256];
    strcpy(buffer, input); // Buffer overflow potential
    // Further exploitation logic
}

int main(int argc, char **argv) {
    if (argc > 1) {
        vulnerableFunction(argv[1]);
    }
    return 0;
}

Detection Methods for CVE-2025-21418

Indicators of Compromise

• Unexpected privilege elevation events
• Unauthorized access logs
• Anomalous process creation activities

Detection Strategies

Leveraging behavior-based threat detection engines that monitor for abnormal process execution and privilege escalation activities can be effective in identifying exploitation attempts.

Monitoring Recommendations

Implement continuous monitoring of Windows driver activities, with specific attention to AFD.sys and process access logs. SentinalOne's autonomous endpoint protection can effectively detect and block real-time exploit attempts using AI-driven analytics.

How to Mitigate CVE-2025-21418

Immediate Actions Required

• Apply available security updates from Microsoft immediately.
• Restrict administrative access where possible.
• Enhance system monitoring for unusual activities.

Patch Information

Microsoft has released patches addressing this vulnerability, which can be found at Microsoft Security Update Guide.

Workarounds

For environments unable to apply patches immediately, disabling unnecessary services related to WinSock and restricting execution permissions can provide temporary mitigation.

# Configuration example
netsh advfirewall set allprofiles state off
# Restrict service execution
sc config afd start= disabled